We created a new dataset of spatially interpolated monthly climate data for global land areas at a very high spatial resolution (approximately 1 km2). We included monthly temperature (minimum, maximum and average), precipitation, solar radiation, vapour pressure and wind speed, aggregated across a target temporal range of 1970–2000, using data from between 9000 and 60 000 weather stations. Weather station data were interpolated using thin-plate splines with covariates including elevation, distance to the coast and three satellite-derived covariates: maximum and minimum land surface temperature as well as cloud cover, obtained with the MODIS satellite platform. Interpolation was done for 23 regions of varying size depending on station density. Satellite data improved prediction accuracy for temperature variables 5–15% (0.07–0.17 °C), particularly for areas with a low station density, although prediction error remained high in such regions for all climate variables. Contributions of satellite covariates were mostly negligible for the other variables, although their importance varied by region. In contrast to the common approach to use a single model formulation for the entire world, we constructed the final product by selecting the best performing model for each region and variable. Global cross-validation correlations were ≥ 0.99 for temperature and humidity, 0.86 for precipitation and 0.76 for wind speed. The fact that most of our climate surface estimates were only marginally improved by use of satellite covariates highlights the importance having a dense, high-quality network of climate station data.

WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas

Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

High resolution information on climatic conditions is essential to many applications in environmental and ecological sciences. Here we present the CHELSA Climatologies at high resolution for the earths land surface areas data of downscaled model output temperature and precipitation estimates of the ERA Interim climatic reanalysis to a high resolution of 30 arc seconds. The temperature algorithm is based on statistical downscaling of atmospheric temperatures. The precipitation algorithm incorporates orographic predictors including wind fields, valley exposition, and boundary layer height with a subsequent bias correction. The resulting data consist of a monthly temperature and precipitation climatology for the years 1979 to 2013. We compare the data derived from the CHELSA algorithm with other standard gridded products and station data from the Global Historical Climate Network. We compare the performance of the new climatologies in species distribution modelling and show that we can increase the accuracy of species range predictions. We further show that CHELSA climatological data has a similar accuracy as other products for temperature but that its predictions of precipitation patterns are better.

/pdf/climatologies-at-high-resolution-for-the-earth-s-land-4462ztbbet.pdf

Climatologies at high resolution for the earth's land surface areas

Wind speeds over the world’s oceans have increased over the past two decades, as have wave heights. Studies of climate change typically consider measurements or predictions of temperature over extended periods of time. Climate, however, is much more than temperature. Over the oceans, changes in wind speed and the surface gravity waves generated by such winds play an important role. We used a 23-year database of calibrated and validated satellite altimeter measurements to investigate global changes in oceanic wind speed and wave height over this period. We find a general global trend of increasing values of wind speed and, to a lesser degree, wave height, over this period. The rate of increase is greater for extreme events as compared to the mean condition.

https://researchbank.swinburne.edu.au/file/bca43746-6f16-4ad2-a4b7-27f8d8d60fed/1/PDF (Published version).pdf

Global trends in wind speed and wave height over the past 25 years

During the past two decades, convective scale models have advanced sufficiently to study the dynamic and microphysical processes associated with mesoscale convective systems. The basic features of these models are that they are non-hydrostatic and include a good representation of microphysical pro­ cesses. The Goddard Cumulus Ensemble (GCE) model has been extensively applied to study cloud-environment interactions, cloud interaction and merg­ ers, air-sea interaction, cloud draft structure and trace gas transport. The GCE model has improved significantly during the past decade. For example, ice-microphysical processes, and solar and infrared radiative transfer pro­ cesses have been included. These model improvements allow the GCE model to study cloud-radiation interaction, cloud-radiation-climate relations and to develop rain retrieval algorithms for Tropical Rainfall Measuring Mission (TRMM). In Part I, a full description of the GCE model is presented, as well as several sensitivity tests associated with its assumptions. In Part II (Simpson and Tao, 1993), we will review GCE model applications to cloud precipitating processes and to the Tropical Rainfall Measuring Mission (TRMM), a joint U.S.-Japan satellite project to measure rain and latent heat release over the global tropics.

Goddard Cumulus Ensemble Model. Part I: Model Description

nteraction among trade winds,terrain, land thermal effects, andthe trade-wind inversion give theHawaiian Islands one of the mostvaried rainfall patterns on Earth.Distinct, persistent patterns of upliftlead to dramatic rainfall gradientsand, together with elevation-relatedtemperature differences, producenearly the full range of climate types.This microcosm of global environ-mental diversity provides a uniquenatural laboratory for world-classresearch on topics such as terres-trial ecosystem carbon dynamics, soilgeochemistry, and the mechanics ofspecies invasion. Knowledge of meanrainfall patterns in Hawai'i is criticallyimportant in support of these researchendeavors as well as for managing andprotecting groundwater and surfacewater resources, controlling and eradicating invasivespecies, protecting and restoring native ecosystems,and planning for the effects of global climate change.The Rainfall Atlas of Hawai'i is a set of digitalmaps of the spatial patterns of 1978-2007 meanmonthly and annual rainfall for the major Hawaiian

Online Rainfall Atlas of Hawai‘i

The rainfall regimes of Taiwan are investigated using the 18-yr European Centre for Medium-Range Weather Forecasts (ECMWF) data (1980–97), the available 38-yr daily rainfall data from 25 conventional surface stations around Taiwan (1961–98), and the 5-yr hourly rainfall data (1994–98) from 249 high-spatial-resolution Automatic Rainfall and Meteorological Telemetry System (ARMTS) stations. Rainfall over the island is usually generated either by transient disturbances embedded in the prevailing monsoon flow or local rainshowers related to terrain or local winds. With the change in the direction of the prevailing winds between the warm and cold seasons as well as a variety of transient subsynoptic disturbances occurring in different seasons (e.g., winter monsoon cold surges, springtime cold fronts, mei-yu fronts in the early summer, typhoons in summer months, and cold fronts in fall) and the presence of the Central Mountain Range, the regional rainfall climate over the island shows large spatial and...

The Rainfall Characteristics of Taiwan

Assessment of wave energy resources in Hawaii

The high-resolution Portable Automated Mesonet data from the Hawaiian Rainband Project are used to document the circulation over the entire island of Hawaii for the first time. It is shown that the surface airflow and rainfall occurrences over the island are strongly modulated by the diurnal heating cycle. Most areas over the island show daytime upslope and nighttime downslope components separated by morning and evening transitions. On the windward slope, the onset of the downslope (upslope) wind during the evening (morning) transition starts on the slopes and progresses downward. The effects of island blocking are also evident. On the windward slopes of Mauna Kea and Mauna Loa, the mean winds are weak (∼1 m s−1) due to flow deceleration. Flow splitting occurs in the Hilo Bay area as the trade winds are forced to move around the island. On the lee side, the trade winds are absent. For stronger trade-wind days, the island blocking is more significant with a higher surface pressure (0.2-0.5 hPa) on...

Diurnal Variation of Surface Airflow and Rainfall Frequencies on the Island of Hawaii

The seasonal variations of heavy rainfall days over Taiwan are analyzed using 6-yr (1997–2002) hourly rainfall data from about 360 rainfall stations, including high-spatial-resolution Automatic Rainfall and Meteorological Telemetry System stations and 25 conventional stations. The seasonal variations and spatial variations of nontyphoon and typhoon heavy rainfall occurrences (i.e., the number of rainfall stations with rainfall rate >15 mm h−1 and daily accumulation >50 mm) are also analyzed. From mid-May to early October, with abundant moisture, potential instability, and the presence of mountainous terrain, nontyphoon heavy rainfall days are frequent (>60%), but only a few stations recorded extremely heavy rainfall (>130 mm day−1) during the passage of synoptic disturbances or the drifting of mesoscale convective systems inland. During the mei-yu season, especially in early June, these events are more widespread than in other seasons. The orographic effects are important in determining the spati...

Yi-Leng Chen

Papers

Online Rainfall Atlas of Hawai‘i

The Rainfall Characteristics of Taiwan

Assessment of wave energy resources in Hawaii

Diurnal Variation of Surface Airflow and Rainfall Frequencies on the Island of Hawaii

Statistics of Heavy Rainfall Occurrences in Taiwan