Showing papers in "Meteorological Applications in 2011"
TL;DR: In this paper, the authors provide an overall review of global precipitation estimation, providing an outline of conventional measurements, the basis of the satellite systems used in the observation of precipitation, and the generation, availability and validation of the derived precipitation products.
Abstract: The quantification of precipitation on a global scale is critical for applications ranging from climate monitoring to water resource management. Conventional observations through surface gauge networks provide the most direct measure of precipitation, although these are very much limited to land areas, with very few in situ measurements over the oceans. Weather radars, although providing a spatial measure of precipitation, are limited in extent and number. Satellite observations offer an unrivalled vantage point to observe precipitation on a global basis. Since precipitation is spatially and temporally highly variable, satellites are able to provide temporal and spatial samples commensurate with many precipitation characteristics. This paper provides an overall review of global precipitation estimation, providing an outline of conventional measurements, the basis of the satellite systems used in the observation of precipitation, and the generation, availability and validation of the derived precipitation products. Finally, future satellite precipitation missions are presented. Copyright © 2011 Royal Meteorological Society
479 citations
TL;DR: The last decade has seen a considerable increase in the amount and availability of remotely sensed data, which can be beneficial for a number of uses, such as urban heat island measurements as discussed by the authors.
Abstract: The last decade has seen a considerable increase in the amount and availability of remotely sensed data. This paper reviews the satellites, sensors and studies relevant to land surface temperature measurements in the context of meteorology and climatology. The focus is on using the thermal infrared part of the electromagnetic spectrum for useful measurements of land surface temperature, which can be beneficial for a number of uses, for example urban heat island measurements. Copyright © 2011 Royal Meteorological Society
284 citations
TL;DR: Overall, the FWI demonstrated several aptitudes related to its potential use as a meteorological fire danger rating index in Mediterranean regions, however, long–term studies are necessary to determine the precise range of each fire danger class according to fire occurrence data.
Abstract: The Fire Weather Index module of the Canadian Forest Fire Danger Rating System (CFFDRS) was evaluated during two consecutive fire seasons in the Mediterranean environment of Crete, Greece. The Duff Moisture Code (DMC), the Drought Code (DC), the Buildup Index (BUI) and the Fire Weather Index (FWI) were highly correlated to fire occurrence but only moderately to area burned. Logistic regression was applied in order to classify the FWI values into fire danger classes appropriate for the Mediterranean environments, as follows: 0–38 Low, 39–48 Moderate, 49–59 High, > 60 Extreme. The new classification was necessary because the existing Canadian fire danger classes were found inapt for the dry and extremely fire prone eastern Mediterranean climate of Crete. After the modification, the fluctuation of the FWI values predicted more successfully the days of high fire risk, as proved by the actual fire occurrence. High correlation was found between measured litter (L layer) moisture values and those predicted by the Fine Fuel Moisture Code (FFMC). The use of an equilibrium duff moisture content value lower than 20% in Mediterranean environments, would probably improve the Duff Moisture Code (DMC) predictions. The Drought Code (DC) was poorly correlated to the upper soil moisture content. Overall, the FWI demonstrated several aptitudes related to its potential use as a meteorological fire danger rating index in Mediterranean regions. However, long–term studies are necessary to determine the precise range of each fire danger class according to fire occurrence data. Copyright © 2010 Royal Meteorological Society
104 citations
TL;DR: In this article, satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy budget of the atmosphere and surface.
Abstract: Satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy budget of the atmosphere and surface. The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system of − 21 Wm−2. The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of − 53 Wm−2. Clouds impact long wave radiation by heating the moist tropical atmosphere (up to around 40 Wm−2 for global annual means) while enhancing the radiative cooling of the atmosphere over other regions, in particular higher latitudes and sub-tropical marine stratocumulus regimes. While clouds act to cool the climate system during the daytime, the cloud greenhouse effect heats the climate system at night. The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed. Copyright © 2011 Royal Meteorological Society
104 citations
TL;DR: An overview of existing satellites and sensors, together with the developed algorithms to retrieve meteorological and climatological parameters, are given and an outlook on new systems planned for the near future is given.
Abstract: Spaceborne remote sensing provides valuable information about the state of the Earth-atmosphere system and its components in an area-wide and continuous manner. Over the past 50 years a range of satellite platforms carrying many different sensors has been constructed to monitor atmospheric parameters used in meteorological and climatological studies, and the information retrieved from satellite-based sensors has greatly enhanced our understanding of the processes and dynamics within the Earth-atmosphere system. The present paper gives an overview of existing satellites and sensors, together with the developed algorithms to retrieve meteorological and climatological parameters. Furthermore, it gives an outlook on new systems planned for the near future. Copyright © 2011 Royal Meteorological Society
86 citations
TL;DR: In this paper, an autoregressive approach was adopted to inspect the time series of monthly maximum temperature (Tmax) over northeast India, which has become stationary on removal of the seasonal and the trend components from the original time series, were generated through Yule-Walker equations.
Abstract: The present paper has adopted an autoregressive approach to inspect the time series of monthly maximum temperature (Tmax) over northeast India. Through autocorrelation analysis the Tmax time series of northeast India is identified as non-stationary, with a seasonality of 12 months, and it is also found to show an increasing trend by using both parametric and non-parametric methods. The autoregressive models of the reduced Tmax time series, which has become stationary on removal of the seasonal and the trend components from the original time series, were generated through Yule–Walker equations. The sixth order autoregressive model (AR(6)) is identified as a suitable representative of the Tmax time series based on the Akaike information criteria, and the prediction potential of AR(6) is also established statistically through Willmott's indices. Subsequently, autoregressive neural network models were generated as a multilayer perceptron, a generalized feed forward neural network and a modular neural network. An autoregressive neural network model of order four (AR-NN(4)), in the form of a modular neural network (MNN), has performed comparably well with that of AR(6) based on the high values of Willmott's indices and the low values of the prediction error. Therefore, AR-NN(4)-MNN will be a better option than AR(6) to forecast a time series, i.e. the monthly Tmax time series of northeast India, because AR-NN(4)-MNN requires fewer predictors for a superior forecast of a time series. Copyright © 2010 Royal Meteorological Society
53 citations
TL;DR: In this article, the authors identify the Indian latitudes most likely to be affected by Stratosphere-troposphere Exchange (STE), the frequency of occurrence of shallow and deep STE events, the depth up to which the ozone from the stratosphere descends into the troposphere during STE events and the resultant trend of ozone in the Troposphere under the possible influence of STE over the 24 years from 1982 to 2006.
Abstract: Stratosphere-troposphere Exchange (STE) is an important factor controlling the budget of ozone in the upper troposphere and lower stratosphere. Studies of STE events in India are so far restricted to co-ordinated campaigns, and measurements over longer periods are relatively scarce. In the light of this observation, this paper aims to identify the Indian latitudes most likely to be affected by STE, the frequency of occurrence of shallow and deep STE events, the depth up to which the ozone from the stratosphere descends into the troposphere during STE events and the resultant trend of ozone in the troposphere under the possible influence of STE over the 24 years from 1982 to 2006. In addition, a case study of the STE of ozone, which occurred during a cut-off low event at Athens, Greece, is presented in order to understand the parameters that may contribute to the evolution of these events. It is concluded that STE plays a minor role in the Indian tropospheric ozone budget. On the whole, the occurrence of STE events in India is found to increase with increase in latitude and occur more frequently during winter followed by summer. The occurrence of deep STE is higher at high latitudes while the occurrence of shallow STE is higher at low latitudes. Copyright © 2011 Royal Meteorological Society
46 citations
TL;DR: In this article, the authors compared the performance of the METEOSAT Second Generation (MSG) images with the MODIS mask for 90.65% and 89.69% of SEVIRI pixels tested, respectively.
Abstract: The Met Office has been using data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellites for nowcasting, assimilation in numerical weather prediction (NWP) and for providing guidance to forecasters since September 2004. This paper describes the cloud mask derived from MSG imagery which is used by all downstream products. The Met Office SEVIRI mask is compared with that of the Nowcasting Satellite Applications Facility (SAFNWC), and with the Moderate Resolution Imaging Spectro-Radiometer (MODIS) cloud mask. These comparisons show good agreement between the cloud masks: the Met Office and SAFNWC masks are in accord with the MODIS mask for 90.65% and 89.69% of SEVIRI pixels tested, respectively. © Crown Copyright 2011. Published with the permission of the Controller of HMSO and the Queen's Printer for Scotland
42 citations
TL;DR: In this paper, the authors investigated the hypothesis that as the climate becomes increasingly milder there will be a reduction in the number of accidents in Sweden during the winter and concluded that using the warmer month as a temporal analogue, the accident rate in Sweden will not fall under current climate change scenarios.
Abstract: Slippery roads due to ice and snow are a major cause of road traffic accidents in Sweden during the winter. This paper investigates the hypothesis that as the climate becomes increasingly milder there will be a reduction in the number of accidents in winter. Two months are compared in this analysis; one colder and drier than average, the other warmer and wetter than average. Despite the differences in weather between the 2 years, there was approximately the same number of accidents in both cases, although the exact cause of these accidents varied. It is concluded that using the warmer month as a temporal analogue, the accident rate in Sweden will not fall under current climate change scenarios. This result is attributed to the fact that drivers become more complacent in milder weather conditions where the risk of slippery roads is reduced. Copyright © 2010 Royal Meteorological Society
42 citations
TL;DR: In this paper, the authors used five years of UK Met Office global model analyses from 1 January 2004 to 31 December 2008 to generate a global hail climatology at 1° latitude by 1° longitude resolution.
Abstract: Five years of UK Met Office global model analyses from 1 January 2004 to 31 December 2008 have been used to generate a global hail climatology at 1° latitude by 1° longitude resolution. Hail has been diagnosed from model vertical profiles of temperature and humidity using a simple algorithm based on a paper by Fawbush and Miller (1953). Results have been compared with published observational climatologies on both a global and regional basis. The model diagnoses compare favourably with the observed data with both orographic and seasonal signals. However, there are differences, and possible reasons for these are discussed. These include limitations of the simple algorithm, the difficulty of observing hail in sparsely populated areas and the problem of population growth influencing the number of hail reports. Copyright © 2011 Royal Meteorological Society and Crown Copyright
36 citations
TL;DR: In this article, the effect of several turbulence parameters during various flow conditions in Owens Valley, educed from coherent Doppler lidar data have been studied, assuming a theoretical model for isotropic wind fields.
Abstract: In this paper, the effect of several turbulence parameters during various flow conditions in Owens Valley, educed from coherent Doppler lidar data have been studied. Radial velocity structure functions are processed to estimate the turbulent kinetic energy (TKE) dissipation rate, integral length scale and velocity variance, assuming a theoretical model for isotropic wind fields. Corrections for turbulence measurements have been considered to address the complications due to inherent volumetric averaging of radial velocity over each range gate, noise of the lidar data, and the assumptions required to estimate effects of smaller scales of motion on turbulence quantities. Using data from the Terrain-induced Rotor Experiment (T-REX) in April–May 2006, vertical profiles of wind and turbulence parameters have been retrieved. During T-REX, unusual valley flows were detected by the lidar data, for example on 19 and 27 March 2006, daytime down-valley and night time up-valley flows, respectively, were observed. This paper focuses on understanding various turbulence parameters during these flow events. Turbulence estimates during daytime down-valley conditions were observed to be constant for most of the day, while for night time up-valley circumstances the turbulence increased steadily as the day progressed. Good comparison was observed between lidar and tower measurements, which validate the lidar turbulence retrieval assumptions. Comparison between TKE estimates from lidar and the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model is also presented. This analysis will be helpful for improving the current turbulence parameterization schemes in COAMPS. Finally, differences and similarities in turbulence measurements between both the flow regimes are discussed. Copyright © 2011 Royal Meteorological Society
TL;DR: In this article, a bispectral thresholding technique involving brightness temperature difference (BTD) between two spectral channels: 3.9 and 10.75 µm, combining radiative transfer simulations and satellite data was used to study 2009 and 2010 fog episodes over the North Indian plains.
Abstract: An algorithm for night time fog detection using satellite data was used to study 2009 and 2010 fog episodes over the North Indian plains. The algorithm employs a bispectral thresholding technique involving brightness temperature difference (BTD) between two spectral channels: 3.9 and 10.75 µm, combining radiative transfer simulations and satellite data. The prolonged fog episode of January 2010 was analysed in detail using this algorithm in conjunction with the meteorological parameters and it was found that upper tropospheric long waves passed over this region during the fog episode. These waves affect the circulation close to the surface and appear to have played an important role in the formation and persistence of fog during 2010. The present thresholding method can be used to monitor night time fog over the Indian subcontinent on an operational basis using the forthcoming geostationary satellite INSAT-3D. Copyright © 2011 Royal Meteorological Society
TL;DR: In this paper, a procedure for decision-making regarding the extent to which a certain geographical region is affected by drought is proposed, which can be used as a support tool by decision-makers.
Abstract: This paper proposes a procedure for decision-making regarding the extent to which a certain geographical region is affected by drought. Professional circles generally recognize the Standardized Precipitation Index (SPI) as a good indicator of a drought event. However, as a result of varying precipitation levels due to various local geographical, climatic, vegetational and other factors, this indicator is determined based on precipitation measurements and different meteorological centres within the same administrative region often generate different SPI values, even when the geographical distance between them is small. During a dry period, various local authorities, ministries of agriculture or governments have to make important decisions about, for example, declaring disasters, subsidizing farmers for certain crops, or providing financial aid to agricultural producers, based on voluminous and diverse data about local precipitation, the yield of various crops, or the condition of the soil. This paper proposes an automated methodology for such decision-making, which can be used as a support tool by decision-makers. The methodology is based on the SPI and statistical pattern recognition methods (dimension reduction and classifier design based on the desired output). The entire procedure is illustrated using Vojvodina, a region in Serbia in the southern portion of the Pannonian Plain, as a case study. The proposed algorithm is not subject to any constraints with regard to geographical locations of regions, their surface areas, or inter-relationships. Copyright © 2010 Royal Meteorological Society
TL;DR: In this paper, the authors used the modified Mann-Kendall test applied on monthly rainfall data for analysis of historical droughts and found statistically significant downward trends at significance level, α = 0.01.
Abstract: Analysis of historical droughts was undertaken by converting observed monthly rainfall over the period
1949–2008 to the Standardized Precipitation Index (SPI). The modified Mann–Kendall test applied on monthly rainfall
showed statistically significant downward trends at significance level, α = 0.01. The Sen’s Slope, estimated from the time-series, revealed statistically significant decreases in annual rainfall ranging from ∼13 to 47 mm year−1. Based on the SPI, drought duration and severity was non-uniform across stations over the 60 year period. The strongest impacted stations were located in western and northern Fiji where rainfall deficiency for the period 1969–1988 led to a dramatic increase in moderate and severe droughts. The return periods of annual rainfall were much longer at these stations relative to those in outer-lying islands. While rainfall increased over the period 1989–2008, the actual amounts did not exceed 1949–1968 totals, confirming a net shift towards drier conditions since the 1950s. This study has demonstrated that SPI can be a useful tool for diagnosis and monitoring meteorological droughts in tropical Pacific islands.
TL;DR: In this article, a review of the geo-engineering approach to tackling climate change is presented, which looks at a variety of global and local approaches to geoengineering covering solar radiation management and carbon cycle engineering and assess the feasibility of the technologies from an engineering perspective.
Abstract: This paper reviews the geo-engineering approach to tackling climate change. The failure of the 15th United Nations Framework Convention on Climate Change Conference of the Parties (COP15) to obtain a legally binding emissions reduction agreement makes the deployment of geo-engineering solutions an increasingly attractive proposition. This review looks at a variety of global and local approaches to geo-engineering covering solar radiation management and carbon cycle engineering and attempts to assess the feasibility of the technologies from an engineering perspective. However, despite the plethora of ideas generated by the science community, it still appears that much work remains to be done in the initial engineering assessment of these techniques and this is a major hurdle to overcome before any geo-engineering scheme can be fully considered. Hence, the paper concludes by calling for the instigation of national and international programmes of research at the feasibility level, to inform discussions regarding future possible deployment of small scale, local geo-engineering and adaptation measures. Copyright © 2011 Royal Meteorological Society
TL;DR: In this article, the authors developed a new convection indicator, called the Combined Instability Index (CII), which calculates the probability of convection based on satellite derived instability indices and moisture as well as orographic lift early in the morning when the sky is as cloud free as possible.
Abstract: Thunderstorms, due to their high frequency of occurrence over southern Africa and their dominant contribution to summer rainfall, are the primary focus of very short range forecasting and nowcasting efforts in South Africa. Most southern African countries are heavily reliant on satellite technology due to the limited number of surface and upper-air observations and the limited availability of numerical model output. In developing tools for the first 12 forecast hours, the South African Weather Service has to address both national and regional needs. The blending of techniques in an optimal manner is essential in achieving this. In this paper a description is given of how the Global Instability Index product derived from the European Meteosat Second Generation Satellite was adapted to fit to South African circumstances using a different numerical model as background information, creating the Regional Instability Indices (RII). The focus of the study is the development of a new convection indicator, called the Combined Instability Index (CII), which calculates the probability of convection based on satellite derived instability indices and moisture as well as orographic lift early in the morning when the sky is as cloud free as possible. The CII is an objective way for operational forecasters to calculate the probability for convection later in the day based on satellite and model data. Early morning CII values were evaluated statistically against the occurrence of lightning as well as against satellite derived precipitation later in the same day. It is shown that the CII not only performs well, but also outperforms the individual RII. The CII will be beneficial to operational forecasters to focus their attention on the area which is most favourable for the development of convection later in the day. Copyright © 2010 Royal Meteorological Society
TL;DR: In this article, a measure of the information added by a probabilistic forecast to that contained in the climatological distribution is presented, which is mathematically closely related to the traditional ignorance score, but is more intuitive.
Abstract: A measure of the information added by a probabilistic forecast to that contained in the climatological distribution is presented in this paper. This measure, called information gain, is mathematically closely related to the traditional ignorance score, but is more intuitive. Its advantages over other scores for probabilistic forecasts are also shown. The information gain score is tested on ECMWF ensemble forecasts of 500 hPa geopotential and 850 hPa temperature. The trends observed are in good agreement with those seen in other verification measures applied to the same data. In particular, the information gain decays with increasing lead time and increases over the years, in agreement with the improvement of the model. Copyright © 2010 Royal Meteorological Society
TL;DR: Lidar is a widely used remote sensing tool for measurements of tropospheric constituents and processes and despite considerable operational challenges, lidars have been deployed in the polar regions to study the unique characteristics of the high-latitude atmosphere as discussed by the authors.
Abstract: The lidar is a widely-used remote sensing tool for measurements of tropospheric constituents and processes. Despite considerable operational challenges, lidars have been deployed in the polar regions to study the unique characteristics of the high-latitude atmosphere. The relevant technologies and techniques used for profiling the polar troposphere are reviewed. Lidars and their measurements are described, from the first single-wavelength lidar aircraft campaign to today's multiple-wavelength, multiple-data product systems and satellite-borne lidars providing large-area polar coverage. Significant advancements in our understanding of tropospheric aerosols, clouds, structure, and trace gases in both the Antarctic and Arctic have been made possible through the use of lidars and these will be discussed. Copyright © 2011 Royal Meteorological Society
TL;DR: This work presents an approach for improving the clear sky TP calculation in two stages, by correcting the slope of this new profile and then using this new slope and land surface temperature, the improved TP for each pixel in the scene is calculated.
Abstract: Retrieving atmospheric temperature profile (TP) data through satellite thermal radiative measurement has gained lots of attentions in recent years. These retrieved profiles may involve some uncertainties. Although different methods have been introduced to minimize these uncertainties, they are time consuming and complicated. This work, based on the available methods, presents an approach for improving the clear sky TP calculation in two stages. In the first stage, a radiosonde mean TP is introduced to the radiation transfer equation and the deviation from this profile is calculated. In the second stage, by correcting the slope of this new profile and then using this new slope and land surface temperature, the improved TP for each pixel in the scene is calculated. A comparison between the model output TP and the one measured by radiosonde in steps of 100 m shows root mean square errors between 0.38 and 3.86 K. This shows considerable improvement compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) products. Copyright © 2010 Royal Meteorological Society
TL;DR: A quality index scheme is proposed which is designed to evaluate the quality of different radar-derived rainfall products including processed radar data and precipitation accumulations.
Abstract: A quality index scheme is proposed which is designed to evaluate the quality of different radar-derived rainfall products including processed radar data and precipitation accumulations. The idea of the quality index scheme is based on selection of quality factors, determination of their quality indices and computation of one final quality index. The factors were selected depending on the particular kind of precipitation field. In the proposed scheme the quality index for each quality factor is determined using regression relationships between quality factors and data errors calculated from rain gauge—radar observation differences. Finally, all the individual quality indices are summarized to a final quality index applying appropriate weights. The quality index is computed for each pixel of radar-derived precipitation field independently. The quality information field obtained in this way is attached to the radar-based precipitation product and can be used to generate the precipitation field as percentiles of probability density functions. Copyright © 2010 Royal Meteorological Society
TL;DR: In this article, the spectral distance between the reference graph and the graphs corresponding to thunderstorms is computed with the data collected during the period 1997-2009 using the most probable vertex distances.
Abstract: The aim of the present study is to forecast thunderstorms over Kolkata (22°32′N, 88°20′E), India, during the pre-monsoon season (April–May) with graph spectral distance and entropy analysis. Graph vertices represent points connected by lines or edges, and lifting condensation level, convective condensation level, level of free convection, freezing level, level of neutral buoyancy and the surface level are taken as the input of the graph vertices. The variation in the most probable distance between the vertices is investigated. The result reveals a particular orientation of the vertex distances for thunderstorm days which is significantly different from the non-thunderstorm days. The reference graphs for thunderstorm and non-thunderstorm days are formed using the most probable vertex distances. The spectral distance between the reference graph and the graphs corresponding to thunderstorms are computed with the data collected during the period 1997–2009. The entropies, or the measure of disorderliness or uncertainty, are estimated for the graph distance matrices. The result shows that the thunderstorm days possess lower distance entropy than the non-thunderstorm days. This indicates that the reference graph that has been constructed for thunderstorms is more consistent. The result further depicts that the forecast accuracy through the present method is 98% with 1 h lead time, whereas the accuracy is 93% with 6 h lead time. The forecast is validated with the India Meteorological Department observations for the years 2007, 2008 and 2009. Copyright © 2011 Royal Meteorological Society
TL;DR: Assessment of long-term wind speed variability using seasonal and annual wind speed data at 32 Iranian synoptic stations from 1960 to 2005 revealed a declining trend in annual wind speeds in the central part of Iran and an increasing trend near the Iranian borders during the study period.
Abstract: According to the Intergovernmental Panel on Climate Change (IPCC), there is a need to carry out in-depth research into the potential for renewable energy as part of international efforts to combat climate change and reduce dependency on fossil fuels. The purpose of this study is to examine long-term wind speed variability using seasonal and annual wind speed data at 32 Iranian synoptic stations from 1960 to 2005 to assess if wind power is a plausible source of renewable energy for Iran. Least-square regression methods and the Kruskal–Wallis test were used to determine the trends and decadal changes in wind speed.
Esfehan province was selected for assessment of the impacts on wind power potential owing to its progressive and forward thinking in exploration of renewable energy. Wind power potential was estimated by fitting a hybrid of the Weibull distribution to the 3 hourly wind data.
This assessment revealed a declining trend in annual wind speeds in the central part of Iran and an increasing trend near the Iranian borders during the study period. The patterns on seasonal and annual scales were generally similar.
The results indicated a similar pattern of wind power variation for stations in Esfehan province, except Ardestan. The monthly wind power potential from November to January and from February to May may be representative of the low and high periods of wind energy, respectively. Consequently, despite the existence of wind speed variability and general declining trends across Esfehan province, wind energy may be explored further over the coming years by employing modern wind turbines that require lower start-up speeds. Copyright © 2010 Royal Meteorological Society
TL;DR: A Climate Aedes Mosquitoes Abundance Model was developed based on the observations to predict the abundance of Aedes mosquitoes in Hong Kong and can provide a useful tool for planning of preventive and control measures against Aedes mosquito in Hong Hong Kong.
Abstract: Aedes albopictus, which can transmit Dengue fever, is one of the common mosquitoes in Hong Kong. To study the effect of weather on the abundance of Aedes mosquitoes in Hong Kong, ovitraps were set up at an unperturbed experimental site for a period of 7 days every month to record the Ovitrap Index, an often-adopted parameter to indicate the abundance of mosquitoes at a site, from July 2007 to June 2009. Analysis of the Ovitrap Indices at the experimental site and the weather elements collected from a nearby automatic weather station in the same period showed that the Ovitrap Indices were highly correlated with the mean air temperature over a 22 day period comprising the preceding 15 days and the 7 days when the ovitraps were in place, as well as the total rainfall over the 15 day period prior to the setting up of the ovitraps. A Climate Aedes Mosquitoes Abundance Model was developed based on the observations to predict the abundance of Aedes mosquitoes in Hong Kong. The model can provide a useful tool for planning of preventive and control measures against Aedes mosquitoes in Hong Kong. Copyright © 2010 Royal Meteorological Society
TL;DR: In this article, two versions of the MOSES model have been used: the Stand-Alone model and the Nimrod-MOSES-PDM model for site-specific modeling.
Abstract: There is an urgent need for improved soil moisture measurements and modelling due to the relevance of surface moisture to the local energy balance (and hence, for example, air temperature forecasting) to flood prediction and to a range of agricultural applications including plant stress and accessibility of heavy machinery onto the land. The UK Met Office Surface Exchanges Scheme (MOSES) represents land surface processes in the Met Office's Unified Model (MetUM). In this research, MOSES was used to simulate soil moisture over an agricultural site in Norfolk, United Kingdom and validate the model estimations against ground truth soil moisture measurements. Two versions of the MOSES model have been used: the Stand-Alone MOSES (for site-specific modelling) and the Nimrod nowcasting products (5 km grid data) based on MOSES Probability Distributed Moisture (MOSES-PDM). The validation results show that both versions of MOSES perform well in soil moisture estimations in general. However, the MOSES model produces a relatively large seasonal bias in the late summer and autumn seasons and the Nimrod-MOSES-PDM tends to underestimate soil moisture in general. A model sensitivity study shows that the soil parameters are most likely to contribute to the errors. In addition, the MOSES model treats the vegetation fraction as a constant throughout a year over agricultural fields, which was found partly to cause the seasonal bias. Recommendations on how to improve MOSES soil moisture estimation are discussed, as are the likely application benefits. Copyright © 2010 Royal Meteorological Society
TL;DR: In this article, the errors introduced into radar estimates of rainfall by making observations at spatial and temporal resolutions that are coarse compared with precipitation systems' characteristic length and time scales are explored.
Abstract: The errors introduced into radar estimates of rainfall by making observations at spatial and temporal resolutions that are coarse compared with precipitation systems' characteristic length and time scales are explored in this study. High resolution (200 m, 50 s) X-band radar data from 48 mid-latitude precipitation events are downgraded progressively in spatial and temporal resolution so that estimates of this sampling error can be made by comparing 10 min rainfall accumulations of this data to accumulations calculated from the original high resolution data. The analysis shows these errors to be of significant magnitude. For 2 km and 5 min sampling, this error varies from 17 to 64% of the mean rainfall accumulation. A relationship is shown between the error introduced from the reduction in spatial resolution and the characteristic length scale of the precipitation system along with a metric of precipitation intensity. Copyright © 2011 Royal Meteorological Society
TL;DR: Both schemes are valuable depending on the specific purpose, the evaluation of the uncertainty of large scale flows or the downscaling of the temperature uncertainty at the level of the local observations.
Abstract: A comparison of the benefits of post-processing ECMWF ensemble forecasts based on a deterministic-like and a regression technique is performed for Belgium. The former is a Linear Model Output Statistics technique (EVMOS) recently developed to allow provision of an appropriate ensemble variability at all lead times, and the latter is the Non-homogeneous Gaussian Regression, NGR. The training of the post-processing techniques is based on the reforecast dataset of ECMWF which covers a period from 1991 to 2007. The EVMOS approach is mainly providing a correction of the systematic error and does not enhance substantially the variance of the ensemble. The application of the NGR method provides an ensemble which encompasses the observations, unlike the EVMOS scheme. However, by taking into account the observational error, the analysis suggests that the ensemble based on the EVMOS post-processing scheme is also found to be consistent. This apparent contradiction is clarified and it turns out that both schemes are valuable depending on the specific purpose, the evaluation of the uncertainty of large scale flows or the downscaling of the temperature uncertainty at the level of the local observations. Copyright © 2010 Royal Meteorological Society
TL;DR: A free tool for the creation of maps at different spatial resolutions for biometeorological and climatological purposes has been developed for use by GIS users and non-specialists alike.
Abstract: Modern GIS tools are inclined to be complex and not well suited to climatological applications. To redress this situation, a free tool for the creation of maps at different spatial resolutions for biometeorological and climatological purposes has been developed for use by GIS users and non-specialists alike. The method produces grids and isolines on maps at the same time using a climate mapping tool (CMT), which employs two different algorithms for deriving isolines from gridded data. CMT allows the creation and mapping based on ASCII and CSV files as well as the import of the most common GIS data file formats. The algorithms and the mapping tool developed can be used for a variety of applications, such as mapping of bioclimate indices. A case study using physiologically equivalent temperature (PET) is presented to demonstrate the features of CMT. Copyright © 2010 Royal Meteorological Society
TL;DR: In this paper, a small but intense convective system affected parts of east Devon during the early hours of 30 October 2008, producing an estimated 200 mm of precipitation, including locally over 20 cm of hail, within a 3 h period.
Abstract: A small but intense convective system affected parts of east Devon during the early hours of 30 October 2008, producing an estimated 200 mm of precipitation, including locally over 20 cm of hail, within a 3 h period. This exceptional storm and its environment are studied here from an observational perspective. Upper air and satellite observations show that the storm developed within an environment characterized by a trend for increasing instability and dynamic forcing for ascent, associated with an approaching upper level cold pool and small positive potential vorticity anomaly. Analysis of surface observations reveals that convective development was strongly focussed by localized, persistent low-level convergence and moisture convergence in the vicinity of a mesoscale surface low pressure area, which rapidly deepened before becoming slow moving over east Devon. Radar, wind profiler and other available observations are used to describe the development and evolution of the convective system, and to identify some additional factors contributing to the exceptional rain- and hail-fall totals. Finally, the role that real-time, simultaneous analysis of these various observation types could play in nowcasting of localized, extreme rainfall events is discussed. © Crown Copyright 2010. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd
TL;DR: In this paper, the performance of two different parameterizations of evapotranspiration when applied to a soil water balance model was evaluated using experimental data of a maize crop to evaluate model accuracy.
Abstract: Soil water content models have huge applications from an agronomic point of view and they are usually used as a sub-model for weather and climate modelling. They are also useful tools for efficient water management irrigation practices. The aim of this investigation is to evaluate the performance of two different parameterizations of evapotranspiration when applied to a soil water balance model. Experimental data of a maize crop is used to evaluate model accuracy. The first methodology proposes a parallel resistance arrangement to represent the latent heat fluxes of the soil surface and the leaves in the canopy layer considering the leaf area index (LAI). The second methodology uses the parameterization proposed by the United Nations Food and Agriculture Organization (FAO), based on the crop coefficient (Kc) and the potential evapotranspiration obtained from the Penman–Monteith equation. The crop was divided into five plots with different irrigation systems according to their phenological stages. The model suitably predicts daily soil water content in five different irrigation systems. Predictions of soil water content using the LAI or Kc methodology tend to overestimate observations. In addition, the model has better predictions using the LAI methodology than the Kc methodology. The root mean square error and the determination coefficient were 0.059 and 0.92, respectively, with the LAI methodology and 0.063 and 0.87, respectively, using the Kc methodology. Copyright © 2010 Royal Meteorological Society
TL;DR: In this article, the authors used a statistical analysis to identify favored locations and the processes through which the winds are associated with the extratropical cyclones over the Southwest Atlantic Ocean.
Abstract: Intense wind events at the southern Brazilian coast cause severe socio-economic losses. Generally, such events have been associated with extratropical cyclones over the Southwest Atlantic Ocean. The purpose of this study is to identify favoured locations and the processes through which the winds are associated with the extratropical cyclones. Using a statistical analysis, the wind speed observed at nine meteorological stations was compared with cyclone depth and offshore distance. Both cyclone depth and location were obtained through an objective procedure of identifying and tracking. Generally, the winds are well associated with the extratropical cyclones only south of 28°S. Altitude also plays an important role in this relationship. Furthermore, the cyclones influence the observed wind field up to 1200 km inland at higher latitude locations. For stations near 28°S, cyclones further from the coast have an influence, but with smaller statistical significance. Copyright © 2010 Royal Meteorological Society