Showing papers on "Precipitation published in 2008"
TL;DR: A conceptual model is proposed that explains this apparent dichotomy of pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds and heavily polluted clouds evaporate much of their water before precipitation can occur.
Abstract: Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.
1,659 citations
TL;DR: In this article, the authors discuss the role of chemical composition and particle size in cloud condensation nucleation processes, and the role that the chemical composition plays in the process of cloud droplet and ice nucleation.
1,347 citations
TL;DR: Observations reveal a distinct link between rainfall extremes and temperature, with heavy rain events increasing during warm periods and decreasing during cold periods, implying that projections of future changes in rainfall extremes in response to anthropogenic global warming may be underestimated.
Abstract: Climate models suggest that extreme precipitation events will become more common in an anthropogenically warmed climate. However, observational limitations have hindered a direct evaluation of model-projected changes in extreme precipitation. We used satellite observations and model simulations to examine the response of tropical precipitation events to naturally driven changes in surface temperature and atmospheric moisture content. These observations reveal a distinct link between rainfall extremes and temperature, with heavy rain events increasing during warm periods and decreasing during cold periods. Furthermore, the observed amplification of rainfall extremes is found to be larger than that predicted by models, implying that projections of future changes in rainfall extremes in response to anthropogenic global warming may be underestimated.
1,273 citations
TL;DR: CloudSat data has been used for cloud profiling radar (CPR) as discussed by the authors, which has been operating since 2 June 2006 and has proven to be remarkably stable since turn-on.
Abstract: [1] This paper reports on the early mission performance of the radar and other major aspects of the CloudSat mission. The Cloudsat cloud profiling radar (CPR) has been operating since 2 June 2006 and has proven to be remarkably stable since turn-on. A number of products have been developed using these space-borne radar data as principal inputs. Combined with other A-Train sensor data, these new observations offer unique, global views of the vertical structure of clouds and precipitation jointly. Approximately 11% of clouds detected over the global oceans produce precipitation that, in all likelihood, reaches the surface. Warm precipitating clouds are both wetter and composed of larger particles than nonprecipitating clouds. The frequency of precipitation increases significantly with increasing cloud depth, and the increased depth and water path of precipitating clouds leads to increased optical depths and substantially more sunlight reflected from precipitating clouds compared to than nonprecipitating warm clouds. The CloudSat observations also provide an authoritative estimate of global ice water paths. The observed ice water paths are larger than those predicted from most climate models. CloudSat observations also indicate that clouds radiatively heat the global mean atmospheric column (relative to clear skies) by about 10 Wm−2. Although this heating appears to be contributed almost equally by solar and infrared absorption, the latter contribution is shown to vary significantly with latitude being influenced by the predominant cloud structures of the different region in questions.
852 citations
TL;DR: Wang et al. as discussed by the authors examined the long-term change in the summer precipitation and associated large-scale monsoon circulation features by using the new dataset of 740 surface stations for recent 54 years (1951-2004) and about 123-yr (1880-2002) records of precipitation in East China.
Abstract: In recent two decades, North and Northeast China have suffered from severe and persistent droughts while the Yangtze River basin and South China have undergone much more significant heavy rainfall/floods events This long-term change in the summer precipitation and associated large-scale monsoon circulation features have been examined by using the new dataset of 740 surface stations for recent 54 years (1951–2004) and about 123-yr (1880–2002) records of precipitation in East China The following new findings have been highlighted: (1) One dominating mode of the inter-decadal variability of the summer precipitation in China is the near-80-yr oscillation Other modes of 12-yr and 30–40-yr oscillations also play an important role in affecting regional inter-decadal variability (2) In recent 54 years, the spatial pattern of the inter-decadal variability of summer precipitation in China is mainly structured with two meridional modes: the dipole pattern and the positive-negative-positive (“+ − + ” pattern) In this period, a regime transition of meridional precipitation mode from “+ − + ” pattern to dipole pattern has been completed In the process of southward movement of much precipitation zone, two abrupt climate changing points that occurred in 1978 and 1992, respectively, were identified (3) Accompanying the afore-described precipitation changes, the East Asian summer monsoon have experienced significant weakening, with northward moisture transport and convergence by the East Asian summer monsoon greatly weakened, thus leading to much deficient moisture supply for precipitation in North China (4) The significant weakening of the component of the tropical upper-level easterly jet (TEJ) has made a dominating contribution to the weakening of the Asian summer monsoon system The cooling in the high troposphere at mid- and high latitudes and the possible warming at low latitude in the Asian region is likely to be responsible for the inter-decadal weakening of the TEJ Copyright © 2007 Royal Meteorological Society
838 citations
TL;DR: In this paper, the authors investigated landfalling atmospheric rivers (ARs) along adjacent north and south-coast regions of western North America from 1997 to 2005 using satellite observations of long, narrow plumes of enhanced integrated water vapor (IWV).
Abstract: The pre-cold-frontal low-level jet within oceanic extratropical cyclones represents the lower-tropospheric component of a deeper corridor of concentrated water vapor transport in the cyclone warm sector. These corridors are referred to as atmospheric rivers (ARs) because they are narrow relative to their length scale and are responsible for most of the poleward water vapor transport at midlatitudes. This paper investigates landfalling ARs along adjacent north- and south-coast regions of western North America. Special Sensor Microwave Imager (SSM/I) satellite observations of long, narrow plumes of enhanced integrated water vapor (IWV) were used to detect ARs just offshore over the eastern Pacific from 1997 to 2005. The north coast experienced 301 AR days, while the south coast had only 115. Most ARs occurred during the warm season in the north and cool season in the south, despite the fact that the cool season is climatologically wettest for both regions. Composite SSM/I IWV analyses showed landfa...
614 citations
TL;DR: In this article, Wang et al. showed that atmospheric heating induced by the rising surface temperatures on the Tibetan Plateau (TP) can enhance East Asian subtropical frontal rainfall, and the mechanism of the linkage was found to be through two distinct Rossby wave trains and the isentropic uplift to the east of the TP.
Abstract: [1] Observational evidence presented here indicates that the surface temperatures on the Tibetan Plateau (TP) have increased by about 1.8°C over the past 50 years. The precipitation pattern that is projected as a result of this warming resembles the leading pattern of precipitation variations in East Asia (EA). Numerical experiments with atmospheric general circulation models show that atmospheric heating induced by the rising TP temperatures can enhance East Asian subtropical frontal rainfall. The mechanism of the linkage is found to be through two distinct Rossby wave trains and the isentropic uplift to the east of the TP, which deform the western Pacific Subtropical High and enhance moisture convergence toward the EA subtropical front. The model calculations suggest that the past changes in TP temperatures and EA summer rainfall may be linked, and that projected future increases in TP temperatures may lead to further enhanced summer frontal rainfall in EA region.
575 citations
TL;DR: In this paper, the authors analyzed global and regional trends in drought for 1950-2000 using a soil moisture-based drought index over global terrestrial areas, excluding Greenland and Antarctica, using a simulation of the terrestrial hydrologic cycle driven by a hybrid reanalysis-observation forcing dataset.
Abstract: Global and regional trends in drought for 1950–2000 are analyzed using a soil moisture–based drought index over global terrestrial areas, excluding Greenland and Antarctica. The soil moisture fields are derived from a simulation of the terrestrial hydrologic cycle driven by a hybrid reanalysis–observation forcing dataset. Drought is described in terms of various statistics that summarize drought duration, intensity, and severity. There is an overall small wetting trend in global soil moisture, forced by increasing precipitation, which is weighted by positive soil moisture trends over the Western Hemisphere and especially in North America. Regional variation is nevertheless apparent, and significant drying over West Africa, as driven by decreasing Sahel precipitation, stands out. Elsewhere, Europe appears to have not experienced significant changes in soil moisture, a trait shared by Southeast and southern Asia. Trends in drought duration, intensity, and severity are predominantly decreasing, but ...
498 citations
TL;DR: In this paper, the authors presented a relatively more detailed analysis of tourism climate by using a modified thermal comfort range for both Taiwan and Western/Middle European conditions, presented by frequency analysis of 10-day intervals.
Abstract: Bioclimate conditions at Sun Moon Lake, one of Taiwan's most popular tourist destinations, are presented Existing tourism-related climate is typically based on mean monthly conditions of air temperature and precipitation and excludes the thermal perception of tourists This study presents a relatively more detailed analysis of tourism climate by using a modified thermal comfort range for both Taiwan and Western/Middle European conditions, presented by frequency analysis of 10-day intervals Furthermore, an integrated approach (climate tourism information scheme) is applied to present the frequencies of each facet under particular criteria for each 10-day interval, generating a time-series of climate data with temporal resolution for tourists and tourism authorities
478 citations
TL;DR: In this article, stable water isotopes (H218O and HDO) have been introduced in a single column model including the Emanuel convection parameterization, and the physical processes underlying the amount effect and propose a methodology to quantify their relative contributions.
Abstract: [1] In the tropics, the proportion of heavier water isotopes in precipitation is anticorrelated with the precipitation amount. The physical processes underlying this so-called amount effect are still poorly understood and quantified. In the present study, stable water isotopes (H218O and HDO) have been introduced in a single column model including the Emanuel convection parameterization. We investigate the physical processes underlying the amount effect and propose a methodology to quantify their relative contributions. We focus on convective processes, since the idealized framework of the single column models does not allow us to consider the effects of large-scale horizontal advections of air masses of different isotopic signatures. We show that two kinds of processes predominantly explain the amount effect: first, the reevaporation of the falling rain and the diffusive exchanges with the surrounding vapor; and second, the recycling of the subcloud layer vapor feeding the convective system by convective fluxes. This highlights the importance of a detailed representation of rain evaporation processes to simulate accurately the isotopic composition of precipitation in the tropics. The variability of the isotopic composition on different timescales (from days to months) is also studied using a unidimensional simulation of the Tropical Ocean–Global Atmosphere–Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) campaign. The amount effect is best observable at intraseasonal or longer timescales. The period of time over which convective activity significantly affects the isotopic composition of precipitation is related to the residence time of water within atmospheric reservoirs.
466 citations
TL;DR: An unprecedented high-temporal-resolution, 100-year data set from the Mississippi River is introduced and it is shown that the large increase in bicarbonate flux that has occurred over the past 50 years is clearly anthropogenically driven.
Abstract: The flow of dissolved inorganic carbon from rivers to the oceans is an important net flux connecting the terrestrial and marine carbon reservoirs. Now a remarkable 100-year record of bicarbonate determinations, made at water treatment plants in the towns of Carrollton and Algiers, has been used as a basis for a study of Mississippi River water and carbon fluxes. Previous work revealed a significant increase the amount of dissolved inorganic carbon, mostly bicarbonate, exported by the Mississippi to the ocean over the past 50 years, but the cause for the increase remained uncertain. The Carrollton/Algiers data, together with sub-watershed and precipitation data, point to a mainly anthropogenic origin — increased bicarbonate discharge from agricultural watersheds that was not balanced by a rise in precipitation. A high temporal resolution, 100-year data set from the Mississippi River is coupled with sub-watershed and precipitation data to reveal that a ∼40 percent increase in flux of bicarbonate that has occurred over the last 50 years is clearly anthropogenically driven. This is caused by an increase in discharge from agricultural watersheds not balanced by a rise in precipitation. It is suggested that land use change and management are arguably more important than changes in climate and carbon dioxide fertilization. The water and dissolved inorganic carbon exported by rivers are important net fluxes that connect terrestrial and oceanic water and carbon reservoirs1. For most rivers, the majority of dissolved inorganic carbon is in the form of bicarbonate. The riverine bicarbonate flux originates mainly from the dissolution of rock minerals by soil water carbon dioxide, a process called chemical weathering, which controls the buffering capacity and mineral content of receiving streams and rivers2. Here we introduce an unprecedented high-temporal-resolution, 100-year data set from the Mississippi River and couple it with sub-watershed and precipitation data to reveal that the large increase in bicarbonate flux that has occurred over the past 50 years (ref. 3) is clearly anthropogenically driven. We show that the increase in bicarbonate and water fluxes is caused mainly by an increase in discharge from agricultural watersheds that has not been balanced by a rise in precipitation, which is also relevant to nutrient and pesticide fluxes to the Gulf of Mexico. These findings demonstrate that alterations in chemical weathering are relevant to improving contemporary biogeochemical budgets. Furthermore, land use change and management were arguably more important than changes in climate and plant CO2 fertilization to increases in riverine water and carbon export from this large region over the past 50 years.
TL;DR: In this paper, the spatial-temporal variations in terrestrial water storage changes (TWSC) from GRACE and compare them to those simulated with the Global Land Data Assimilation System (GLDAS).
Abstract: Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided first estimates of land water storage variations by monitoring the time-variable component of Earth's gravity field. Here we characterize spatial-temporal variations in terrestrial water storage changes (TWSC) from GRACE and compare them to those simulated with the Global Land Data Assimilation System (GLDAS). Additionally, we use GLDAS simulations to infer how TWSC is partitioned into snow, canopy water and soil water components, and to understand how variations in the hydrologic fluxes act to enhance or dissipate the stores. Results quantify the range of GRACE-derived storage changes during the studied period and place them in the context of seasonal variations in global climate and hydrologic extremes including drought and flood, by impacting land memory processes. The role of the largest continental river basins as major locations for freshwater redistribution is highlighted. GRACE-based storage changes are in good agreement with those obtained from GLDAS simulations. Analysis of GLDAS-simulated TWSC illustrates several key characteristics of spatial and temporal land water storage variations. Global averages of TWSC were partitioned nearly equally between soil moisture and snow water equivalent, while zonal averages of TWSC revealed the importance of soil moisture storage at low latitudes and snow storage at high latitudes. Evapotranspiration plays a key role in dissipating globally averaged terrestrial water storage. Latitudinal averages showed how precipitation dominates TWSC variations in the tropics, evapotranspiration is most effective in the midlatitudes, and snowmelt runoff is a key dissipating flux at high latitudes. Results have implications for monitoring water storage response to climate variability and change, and for constraining land model hydrology simulations.
TL;DR: In this article, the authors presented estimates of water resources changes in three river basins in the Hindukush-Karakorum-Himalaya (HKH) region associated with climate change.
TL;DR: In the last half of the 20th century, cumulative annual discharge from 137 representative rivers (watershed areas ranging from 0.3 to 6300 × 10 3 ǫ km 2 ) to the global ocean remained constant, although annual discharge of about one-third of these rivers changed by more than 30% as mentioned in this paper.
TL;DR: In this paper, a six-member ensemble of twentieth-century simulations with changes to only time-evolving global distributions of black carbon aerosols in a global coupled climate model is analyzed to study the effects of Black carbon (BC) aerosols on the Indian monsoon.
Abstract: A six-member ensemble of twentieth-century simulations with changes to only time-evolving global distributions of black carbon aerosols in a global coupled climate model is analyzed to study the effects of black carbon (BC) aerosols on the Indian monsoon. The BC aerosols act to increase lower-tropospheric heating over South Asia and reduce the amount of solar radiation reaching the surface during the dry season, as noted in previous studies. The increased meridional tropospheric temperature gradient in the premonsoon months of March–April–May (MAM), particularly between the elevated heat source of the Tibetan Plateau and areas to the south, contributes to enhanced precipitation over India in those months. With the onset of the monsoon, the reduced surface temperatures in the Bay of Bengal, Arabian Sea, and over India that extend to the Himalayas act to reduce monsoon rainfall over India itself, with some small increases over the Tibetan Plateau. Precipitation over China generally decreases due to...
TL;DR: In this paper, a Lagrangian diagnostic for identifying the sources of water vapor for precipitation over the Greenland ice sheet for 30 selected months with pronounced positive, negative and neutral North Atlantic Oscillation (NAO) index, using the European Centre for Medium-Range Weather Forecasts' ERA-40 reanalysis data.
Abstract: [1] We present a new Lagrangian diagnostic for identifying the sources of water vapor for precipitation. Unlike previous studies, the method allows for a quantitative demarcation of evaporative moisture sources. This is achieved by taking into account the temporal sequence of evaporation into and precipitation from an air parcel during transport, as well as information on its proximity to the boundary layer. The moisture source region diagnostic was applied to trace the origin of water vapor for winter precipitation over the Greenland ice sheet for 30 selected months with pronounced positive, negative, and neutral North Atlantic Oscillation (NAO) index, using the European Centre for Medium-Range Weather Forecasts' ERA-40 reanalysis data. The North Atlantic and the Nordic seas proved to be the by far dominant moisture sources for Greenland. The location of the identified moisture sources in the North Atlantic basin strongly varied with the NAO phase. More specifically, the method diagnosed a shift from sources north of Iceland during NAO positive months to a maximum in the southeastern North Atlantic for NAO negative months, qualitatively consistent with changes in the concurrent large-scale mean flow. More long-range moisture transport was identified during the NAO negative phase, leading to the advection of moisture from more southerly locations. Different regions of the Greenland ice sheet experience differing changes in the average moisture source locations; variability was largest in the north and west of Greenland. The strong moisture source variability for Greenland winter precipitation with the NAO found here can have a large impact on the stable isotope composition of Greenland precipitation and hence can be important for the interpretation of stable isotope data from ice cores. In a companion paper, the implications of the present results are further explored in that respect.
TL;DR: Results indicate that semi-arid grasslands are capable of responding immediately and substantially to forecast shifts to more extreme precipitation patterns, and also indicate that soil moisture data indicated that larger events led to greater soil water content and likely permitted moisture penetration to deeper in the soil profile.
Abstract: Water availability is the primary constraint to aboveground net primary productivity (ANPP) in many terrestrial biomes, and it is an ecosystem driver that will be strongly altered by future climate change. Global circulation models predict a shift in precipitation patterns to growing season rainfall events that are larger in size but fewer in number. This “repackaging” of rainfall into large events with long intervening dry intervals could be particularly important in semi-arid grasslands because it is in marked contrast to the frequent but small events that have historically defined this ecosystem. We investigated the effect of more extreme rainfall patterns on ANPP via the use of rainout shelters and paired this experimental manipulation with an investigation of long-term data for ANPP and precipitation. Experimental plots (n = 15) received the long-term (30-year) mean growing season precipitation quantity; however, this amount was distributed as 12, six, or four events applied manually according to seasonal patterns for May–September. The long-term mean (1940–2005) number of rain events in this shortgrass steppe was 14 events, with a minimum of nine events in years of average precipitation. Thus, our experimental treatments pushed this system beyond its recent historical range of variability. Plots receiving fewer, but larger rain events had the highest rates of ANPP (184 ± 38 g m−2), compared to plots receiving more frequent rainfall (105 ± 24 g m−2). ANPP in all experimental plots was greater than long-term mean ANPP for this system (97 g m−2), which may be explained in part by the more even distribution of applied rain events. Soil moisture data indicated that larger events led to greater soil water content and likely permitted moisture penetration to deeper in the soil profile. These results indicate that semi-arid grasslands are capable of responding immediately and substantially to forecast shifts to more extreme precipitation patterns.
TL;DR: In this paper, the authors used a large data set (more than six years) of rainfall measurements from a dense network of 50 rain gauges deployed over an area of about 135 km2 in the Brue catchment (southwestern England) in the UK.
Abstract: [1] Rain gauge networks provide rainfall measurements with a high degree of accuracy at specific locations but, in most cases, the instruments are too sparsely distributed to accurately capture the high spatial and temporal variability of precipitation systems. Radar and satellite remote sensing of rainfall has become a viable approach to address this problem effectively. However, among other sources of uncertainties, the remote-sensing based rainfall products are unavoidably affected by sampling errors that need to be evaluated and characterized. Using a large data set (more than six years) of rainfall measurements from a dense network of 50 rain gauges deployed over an area of about 135 km2 in the Brue catchment (south-western England), this study sheds some light on the temporal and spatial sampling uncertainties: the former are defined as the errors resulting from temporal gaps in rainfall observations, while the latter as the uncertainties due to the approximation of an areal estimate using point measurements. It is shown that the temporal sampling uncertainties increase with the sampling interval according to a scaling law and decrease with increasing averaging area with no strong dependence on local orography. On the other hand, the spatial sampling uncertainties tend to decrease for increasing accumulation time, with no strong dependence on location of the gauge within the pixel or on the gauge elevation. For the evaluation of high resolution satellite rainfall products, a simple rule is proposed for the number of rain gauges required to estimate areal rainfall with a prescribed accuracy. Additionally, a description is given of the characteristics of the rainfall process in the area in terms of spatial correlation.
TL;DR: In this paper, simulated daily discharge derived from a relatively high-resolution (approximately 1.1-degree) general circulation model was used to investigate future projections of extremes in river discharge under global warming.
Abstract: Simulated daily discharge derived from a relatively high-resolution (approximately 1.1-degree) general circulation model was used to investigate future projections of extremes in river discharge under global warming. The frequency of floods was projected to increase over many regions, except those including North America and central to western Eurasia. The drought frequency was projected to increase globally, while regions such as northern high latitudes, eastern Australia, and eastern Eurasia showed a decrease or no significant changes. Changes in flood and drought are not explained simply by changes in annual precipitation, heavy precipitation, or differences between precipitation and evapotranspiration. Several regions were projected to have increases in both flood frequency and drought frequency. Such regions show a decrease in the number of precipitation days, but an increase in days with heavy rain. Several regions show shifts in the flood season from springtime snowmelt to the summer perio...
TL;DR: In this paper, the authors analyzed the water content in the atmosphere over the Tibetan Plateau, the atmospheric circulations and transports of water vapor to this part of the world, and the trend of the water vapor supply.
Abstract: [1] A large amount of water is stored in the world's highest and largest plateau, the Tibetan Plateau, in the forms of glaciers, snowpacks, lakes, and rivers. It is vital to understand where these waters come from and whether the supply to these water resources has been experiencing any changes during recent global warming. Here we show the maintenance of water content in the atmosphere over the Tibetan Plateau, the atmospheric circulations and transports of water vapor to this part of the world, and the trend of the water vapor supply. The Tibetan Plateau serves as a role of “the world water tower”, and its land-ocean-atmosphere interaction provides a profound impact on the global natural and climate environment. The analyses of a half-century time series of atmospheric water vapor, precipitation, and surface temperature indicate that the atmospheric supply to this water tower presents an increasing trend under recent global warming condition.
TL;DR: In this paper, an integrated hydrologic model called GSFLOW (ground-water and surface-water FLOW) was developed to simulate coupled ground water and surface water resources.
Abstract: The need to assess the effects of variability in climate, biota, geology, and human activities on water availability and flow requires the development of models that couple two or more components of the hydrologic cycle. An integrated hydrologic model called GSFLOW (Ground-water and Surface-water FLOW) was developed to simulate coupled ground-water and surface-water resources. The new model is based on the integration of the U.S. Geological Survey Precipitation-Runoff Modeling System (PRMS) and the U.S. Geological Survey Modular Ground-Water Flow Model (MODFLOW). Additional model components were developed, and existing components were modified, to facilitate integration of the models. Methods were developed to route flow among the PRMS Hydrologic Response Units (HRUs) and between the HRUs and the MODFLOW finite-difference cells. This report describes the organization, concepts, design, and mathematical formulation of all GSFLOW model components. An important aspect of the integrated model design is its ability to conserve water mass and to provide comprehensive water budgets for a location of interest. This report includes descriptions of how water budgets are calculated for the integrated model and for individual model components. GSFLOW provides a robust modeling system for simulating flow through the hydrologic cycle, while allowing for future enhancements to incorporate other simulation techniques.
TL;DR: In this paper, the authors demonstrate that the primary climatological features of the tropical precipitation and low-level circulation can be represented by a three-parameter metrics: the annual mean and two major modes of annual variation, namely, a solstitial mode and an equinoctial asymmetric mode.
TL;DR: The results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.
Abstract: Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7 degrees C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.
TL;DR: In this article, the authors explored the relationship between winter air temperature, precipitation and soil freezing for 31 sites in Canada, ranging from the temperate zone to the high Arctic, and found that changes in winter temperature will have a much stronger effect on annual soil freezing days and freeze-thaw cycles than changes in total precipitation.
Abstract: Changes to soil freezing dynamics with climate change can modify ecosystem carbon and nutrient losses. Soil freezing is influenced strongly by both air temperature and insulation by the snowpack, and it has been hypothesized that winter climate warming may lead to increased soil freezing as a result of reduced snowpack thickness. I used weather station data to explore the relationships between winter air temperature, precipitation and soil freezing for 31 sites in Canada, ranging from the temperate zone to the high Arctic. Inter-annual climate variation and associated soil temperature variation over the last 40 years were examined and used to interpolate the effects of projected climate change on soil freezing dynamics within sites using linear regression models. Annual soil freezing days declined with increasing mean winter air temperature despite decreases in snow depth and cover, and reduced precipitation only increased annual soil freezing days in the warmest sites. Annual soil freeze–thaw cycles increased in both warm and dry winters, although the effects of precipitation were strongest in sites that experience low mean winter precipitation. Overall, it was projected that by 2050, changes in winter temperature will have a much stronger effect on annual soil freezing days and freeze–thaw cycles than changes in total precipitation, with sites close to but below freezing experiencing the largest changes in soil freezing days. These results reveal that experimental data relevant to the effects of climate changes on soil freezing dynamics and changes in associated soil physical and biological processes are lacking.
TL;DR: In this article, the dynamics and microphysics of clouds observed during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall, and Climate (LBA-SMOCC) campaign, as well as extremely continental and extremely maritime clouds, are performed using an updated version of the Hebrew University spectral microphysical cloud model (HUCM).
Abstract: The simulation of the dynamics and the microphysics of clouds observed during the Large-Scale Biosphere–Atmosphere Experiment in Amazonia—Smoke, Aerosols, Clouds, Rainfall, and Climate (LBA–SMOCC) campaign, as well as extremely continental and extremely maritime clouds, is performed using an updated version of the Hebrew University spectral microphysics cloud model (HUCM). A new scheme of diffusional growth allows the reproduction of in situ–measured droplet size distributions including those formed in extremely polluted air. It was shown that pyroclouds forming over the forest fires can precipitate. Several mechanisms leading to formation of precipitation from pyroclouds are considered. The mechanisms by which aerosols affect the microphysics and precipitation of warm cloud-base clouds have been investigated by analyzing the mass, heat, and moisture budgets. The increase in aerosol concentration increases both the generation and the loss of the condensate mass. In the clouds developing in dry ai...
13 Aug 2008
TL;DR: In this article, the application of trivariate thin-plate smoothing splines to the interpolation of daily weather data is investigated, and the method is used to develop spatial models of daily minimum and maximum temperature and daily precipitation for all of Canada.
Abstract: Abstract The application of trivariate thin-plate smoothing splines to the interpolation of daily weather data is investigated. The method was used to develop spatial models of daily minimum and maximum temperature and daily precipitation for all of Canada, at a spatial resolution of 300 arc s of latitude and longitude, for the period 1961–2003. Each daily model was optimized automatically by minimizing the generalized cross validation. The fitted trivariate splines incorporated a spatially varying dependence on ground elevation and were able to adapt automatically to the large variation in station density over Canada. Extensive quality control measures were performed on the source data. Error estimates for the fitted surfaces based on withheld data across southern Canada were comparable to, or smaller than, errors obtained by daily interpolation studies elsewhere with denser data networks. Mean absolute errors in daily maximum and minimum temperature averaged over all years were 1.1° and 1.6°C, respectiv...
TL;DR: In this article, an event-based method of analyzing the measurements from multiple satellite sensors is presented by using observations of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR), Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and Lightning Imaging System (LIS).
Abstract: An event-based method of analyzing the measurements from multiple satellite sensors is presented by using observations of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR), Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and Lightning Imaging System (LIS). First, the observations from PR, VIRS, TMI, and LIS are temporally and spatially collocated. Then the cloud and precipitation features are defined by grouping contiguous pixels using various criteria, including surface rain, cold infrared, or microwave brightness temperature. The characteristics of measurements from different sensors inside these features are summarized. Then, climatological descriptions of many properties of the identified features are generated. This analysis method condenses the original information of pixellevel measurements into the properties of events, which can greatly increase the efficiency of searching and sorting the observed historical events. Using the TRMM cloud and precipitation feature database, the regional variations of rainfall contribution by features with different size, intensity, and PR reflectivity vertical structure are shown. Above the freezing level, land storms tend to have larger 20-dBZ area and reach higher altitude than is the case for oceanic storms, especially those land storms over central Africa. Horizontal size and the maximum reflectivity of oceanic storms decrease with altitude. For land storms, these intensity measures increase with altitude between 2 km and the freezing level and decrease more slowly with altitude above the freezing level than for ocean storms.
TL;DR: In this article, high-resolution observations and regional climate model simulations reveal that precipitation over the Maritime Continent is mostly concentrated over islands, reinforced by mountain-valley winds and further amplified by the cumulus merger processes.
Abstract: High-resolution observations and regional climate model simulations reveal that precipitation over the Maritime Continent is mostly concentrated over islands. Analysis of the diurnal cycles of precipitation and winds indicates that this is predominantly caused by sea-breeze convergence over islands, reinforced by mountain–valley winds and further amplified by the cumulus merger processes. Comparison of a regional climate model control simulation to a flat-island run and an all-ocean run demonstrates that the underrepresentation of islands and terrain in the Maritime Continent weakens the atmospheric disturbance associated with the diurnal cycle, and hence underestimates precipitation. The implication of these regional modeling results is that systematic errors in coarse-resolution global circulation models probably result from insufficient representation of land–sea breezes associated with the complex topography in the Maritime Continent. It is found that precipitation in the Maritime Continent, ...
TL;DR: Wang et al. as discussed by the authors investigated spatial and temporal patterns of trends of the precipitation maxima (defined as the annual/seasonal maximum precipitation) in the Yangtze River basin for 1960-2005 using Mann-Kendall trend test, and explored association of changing patterns of precipitation maximima with large-scale circulation using NCEP/NCAR reanalysis data.
University of Oklahoma1, Potsdam Institute for Climate Impact Research2, Centre national de la recherche scientifique3, University of Colorado Boulder4, Technical University of Denmark5, University of Massachusetts Boston6, Oak Ridge National Laboratory7, Colorado State University8, Swedish University of Agricultural Sciences9, Woods Hole Research Center10, United States Forest Service11
TL;DR: In this article, the effects of climate warming, seasonality, and CO2 levels on seven ecosystems, including forests, grasslands, and heathlands in different climate zones, were investigated.
Abstract: Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2 ]( C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the threeway interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor’s effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor’s effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes.