scholarly journals Evaluation of Regional Climatic Model Simulated Aerosol Optical Properties over South Africa Using Ground-Based and Satellite Observations

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
M. Tesfaye ◽  
J. Botai ◽  
V. Sivakumar ◽  
G. Mengistu Tsidu
Keyword(s):  
South Africa ◽  
Standard Deviation ◽  
Climate Model ◽  
Regional Climate ◽  
Dust Emission ◽  
Aerosol Extinction ◽  
Aerosol Optical Property ◽  
Area Of Interest ◽  
Good Ability ◽  
Simulated Precipitation

The present study evaluates the aerosol optical property computing performance of the Regional Climate Model (RegCM4) which is interactively coupled with anthropogenic-desert dust schemes, in South Africa. The validation was carried out by comparing RegCM4 estimated: aerosol extinction coefficient profile, Aerosol Optical Depth (AOD), and Single Scattering Albedo (SSA) with AERONET, LIDAR, and MISR observations. The results showed that the magnitudes of simulated AOD at the Skukuza station (24°S, 31°E) are within the standard deviation of AERONET and ±25% of MISR observations. Within the latitudinal range of 26.5°S to 24.5°S, simulated AOD and SSA values are within the standard deviation of MISR retrievals. However, within the latitude range of 33.5°S to 27°S, the model exhibited enhanced AOD and SSA values when compared with MISR observations. This is primarily associated with the dry bias in simulated precipitation that leads to the overestimation of dust emission and underestimation of aerosol wet deposition. With respect to LIDAR, the model performed well in capturing the major aerosol extinction profiles. Overall, the results showed that RegCM4 has a good ability in reproducing the major observational features of aerosol optical fields over the area of interest.

scholarly journals Validation of the HIRHAM-Simulated Indian Summer Monsoon Circulation

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Stefan Polanski ◽  
Annette Rinke ◽  
Klaus Dethloff
Keyword(s):  
Summer Monsoon ◽  
Climate Model ◽  
Regional Climate ◽  
Horizontal Resolution ◽  
Monsoon Circulation ◽  
Data Sets ◽  
Data Set ◽  
Topographic Features ◽  
Temperature And Precipitation ◽  
Simulated Precipitation

The regional climate model HIRHAM has been applied over the Asian continent to simulate the Indian monsoon circulation under present-day conditions. The model is driven at the lateral and lower boundaries by European reanalysis (ERA40) data for the period from 1958 to 2001. Simulations with a horizontal resolution of 50 km are carried out to analyze the regional monsoon patterns. The focus in this paper is on the validation of the long-term summer monsoon climatology and its variability concerning circulation, temperature, and precipitation. Additionally, the monsoonal behavior in simulations for wet and dry years has been investigated and compared against several observational data sets. The results successfully reproduce the observations due to a realistic reproduction of topographic features. The simulated precipitation shows a better agreement with a high-resolution gridded precipitation data set over the central land areas of India and in the higher elevated Tibetan and Himalayan regions than ERA40.

scholarly journals Dust emission size distribution impact on aerosol budget and radiative forcing over the Mediterranean region: a regional climate model approach

2012 ◽  
Vol 12 (21) ◽  
pp. 10545-10567 ◽  
Author(s):  
P. Nabat ◽  
F. Solmon ◽  
M. Mallet ◽  
J. F. Kok ◽  
S. Somot
Keyword(s):  
Size Distribution ◽  
Radiative Forcing ◽  
Mediterranean Basin ◽  
Climate Model ◽  
Regional Climate ◽  
Dust Emission ◽  
Dust Deposition ◽  
The Mediterranean ◽  
Dust Distribution ◽  
The Mediterranean Basin

Abstract. The present study investigates the dust emission and load over the Mediterranean basin using the coupled chemistry–aerosol–regional climate model RegCM-4. The first step of this work focuses on dust particle emission size distribution modeling. We compare a parameterization in which the emission is based on the individual kinetic energy of the aggregates striking the surface to a recent parameterization based on an analogy with the fragmentation of brittle materials. The main difference between the two dust schemes concerns the mass proportion of fine aerosol that is reduced in the case of the new dust parameterization, with consequences for optical properties. At the episodic scale, comparisons between RegCM-4 simulations, satellite and ground-based data show a clear improvement using the new dust distribution in terms of aerosol optical depth (AOD) values and geographic gradients. These results are confirmed at the seasonal scale for the investigated year 2008. This change of dust distribution has sensitive impacts on the simulated regional dust budget, notably dry dust deposition and the regional direct aerosol radiative forcing over the Mediterranean basin. In particular, we find that the new size distribution produces a higher dust deposition flux, and smaller top of atmosphere (TOA) dust radiative cooling. A multi-annual simulation is finally carried out using the new dust distribution over the period 2000–2009. The average SW radiative forcing over the Mediterranean Sea reaches −13.6 W m−2 at the surface, and −5.5 W m−2 at TOA. The LW radiative forcing is positive over the basin: 1.7 W m−2 on average over the Mediterranean Sea at the surface, and 0.6 W m−2 at TOA.

scholarly journals Increasing Arabian dust activity and the Indian summer monsoon

2015 ◽  
Vol 15 (14) ◽  
pp. 8051-8064 ◽  
Author(s):  
F. Solmon ◽  
V. S. Nair ◽  
M. Mallet
Keyword(s):  
Radiative Forcing ◽  
Arabian Sea ◽  
Climate Model ◽  
Regional Climate ◽  
Dust Emission ◽  
Summer Precipitation ◽  
Southern India ◽  
Precipitation Trend ◽  
Relative Role ◽  
Precipitation Trends

Abstract. Over the past decade, aerosol optical depth (AOD) observations based on satellite and ground measurements have shown a significant increase over Arabia and the Arabian Sea, attributed to an intensification of regional dust activity. Recent studies have also suggested that west Asian dust forcing could induce a positive response of Indian monsoon precipitations on a weekly timescale. Using observations and a regional climate model including interactive slab-ocean and dust aerosol schemes, the present study investigates possible climatic links between the increasing June–July–August–September (JJAS) Arabian dust activity and precipitation trends over southern India during the 2000–2009 decade. Meteorological reanalysis and AOD observations suggest that the observed decadal increase of dust activity and a simultaneous intensification of summer precipitation trend over southern India are both linked to a deepening of JJAS surface pressure conditions over the Arabian Sea. In the first part of the study, we analyze the mean climate response to dust radiative forcing over the domain, discussing notably the relative role of Arabian vs. Indo-Pakistani dust regions. In the second part of the study, we show that the model skills in reproducing regional dynamical patterns and southern Indian precipitation trends are significantly improved only when an increasing dust emission trend is imposed on the basis of observations. We conclude that although interannual climate variability might primarily determine the observed regional pattern of increasing dust activity and precipitation during the 2000–2009 decade, the associated dust radiative forcing might in return induce a critical dynamical feedback contributing to enhancing regional moisture convergence and JJAS precipitations over southern India.

scholarly journals Validation of a High-Resolution Version of the Regional Climate Model RegCM3 over the Carpathian Basin

2011 ◽  
Vol 12 (1) ◽  
pp. 84-100 ◽  
Author(s):  
Csaba Torma ◽  
Erika Coppola ◽  
Filippo Giorgi ◽  
Judit Bartholy ◽  
Rita Pongrácz
Keyword(s):  
High Resolution ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Model Performance ◽  
Region Of Interest ◽  
Carpathian Basin ◽  
Temperature And Precipitation ◽  
Area Of Interest ◽  
Wide Range

Abstract This paper presents a validation study for a high-resolution version of the Regional Climate Model version 3 (RegCM3) over the Carpathian basin and its surroundings. The horizontal grid spacing of the model is 10 km—the highest reached by RegCM3. The ability of the model to capture temporal and spatial variability of temperature and precipitation over the region of interest is evaluated using metrics spanning a wide range of temporal (daily to climatology) and spatial (inner domain average to local) scales against different observational datasets. The simulated period is 1961–90. RegCM3 shows small temperature biases but a general overestimation of precipitation, especially in winter; although, this overestimate may be artificially enhanced by uncertainties in observations. The precipitation bias over the Hungarian territory, the authors’ main area of interest, is mostly less than 20%. The model captures well the observed late twentieth-century decadal-to-interannual and interseasonal variability. On short time scales, simulated daily temperature and precipitation show a high correlation with observations, with a correlation coefficient of 0.9 for temperature and 0.6 for precipitation. Comparison with two Hungarian station time series shows that the model performance does not degrade when going to the 10-km gridpoint scale. Finally, the model reproduces the spatial distribution of dry and wet spells over the region. Overall, it is assessed that this high-resolution version of RegCM3 is of sufficiently good quality to perform climate change experiments over the Carpathian region—and, in particular, the Hungarian territory—for application to impact and adaptation studies.

scholarly journals Long-Term Changes in the Climatology of Transient Inverted Troughs over the North American Monsoon Region and Their Effects on Precipitation

2016 ◽  
Vol 29 (17) ◽  
pp. 6037-6064 ◽  
Author(s):  
Timothy M. Lahmers ◽  
Christopher L. Castro ◽  
David K. Adams ◽  
Yolande L. Serra ◽  
John J. Brost ◽  
...  
Keyword(s):  
North American ◽  
Climate Model ◽  
Regional Climate ◽  
Track Density ◽  
North American Monsoon ◽  
Northwest Mexico ◽  
The North ◽  
Simulated Precipitation ◽  
Precipitation Estimates ◽  
Resolution Model

Abstract Transient inverted troughs (IVs) are a trigger for severe weather during the North American monsoon (NAM) in the southwest contiguous United States (CONUS) and northwest Mexico. These upper-tropospheric disturbances enhance the synoptic-scale and mesoscale environment for organized convection, increasing the chances for microbursts, straight-line winds, blowing dust, and flash flooding. This work considers changes in the track density climatology of IVs between 1951 and 2010. IVs are tracked as potential vorticity (PV) anomalies on the 250-hPa surface from a regional climate model that dynamically downscales the NCEP–NCAR Reanalysis 1. Late in the NAM season, a significant increase in IV track density over the 60-yr period is observed over Southern California and western Arizona, coupled with a slight decrease over northwest Mexico. Changes in precipitation are evaluated on days when an IV is observed and days without an IV, using high-resolution model-simulated precipitation estimates and CPC gridded precipitation observations. Because of changes in the spatial distribution of IVs during the 1951–2010 analysis period, which are associated with a strengthening of the monsoon ridge, it is suggested that IVs have played a lesser role in the initiation and organization of monsoon convection in the southwest CONUS during recent warm seasons.

scholarly journals Increasing Arabian dust activity and the Indian Summer Monsoon

2015 ◽  
Vol 15 (4) ◽  
pp. 4879-4907 ◽  
Author(s):  
F. Solmon ◽  
V. S. Nair ◽  
M. Mallet
Keyword(s):  
Radiative Forcing ◽  
Arabian Sea ◽  
Climate Model ◽  
Regional Climate ◽  
Dust Emission ◽  
Summer Precipitation ◽  
Southern India ◽  
Precipitation Trend ◽  
The Past ◽  
June July

Abstract. Over the past decade, Aerosol Optical Depth (AOD) observations based on satellite and ground measurements have shown a significant increase over Arabia and the Arabian Sea, attributed to an intensification of regional dust activity. Recent studies have also suggested that west Asian dust forcing could induce a positive response of Indian monsoon precipitations on a weekly time scale. Using observations and a regional climate model including interactive slab ocean and dust aerosol schemes, the present study investigates possible climatic links between the increasing June-July-August-September (JJAS) Arabian dust activity and precipitation trends over southern India during the 2000–2009 decade. Meteorological reanalysis and AOD observations suggest that the observed decadal increase of dust activity and a simultaneous intensification of summer precipitation trend over southern India are both linked to a deepening of JJAS surface pressure conditions over the Arabian Sea. We show that the model skills in reproducing this trends and patterns are significantly improved only when an increasing dust emission trend is imposed on the basis of observations. We conclude that although climate variability might primarily determine the observed regional pattern of increasing dust activity and precipitation during the 2000–2009 decade, the associated dust radiative forcing might however induce a critical dynamical feedback contributing to enhanced regional moisture convergence and JJAS precipitation over Southern India.

scholarly journals Assessment of Various Bias Correction Methods on Precipitation of Regional Climate Model and Future Projection

2021 ◽  
Author(s):  
Gunavathi S ◽  
Selvasidhu R
Keyword(s):  
Regional Climate Model ◽  
Bias Correction ◽  
Climate Model ◽  
Rainwater Harvesting ◽  
Regional Climate ◽  
Power Transformation ◽  
Northeast Monsoon ◽  
Correction Technique ◽  
Simulated Precipitation ◽  
The Future

Abstract The application of regional climate model simulations (RCMs) in climate change impact studies is challengeable due to the risk of possible biases. Some sort of correction needs to be done prior to the application of RCM simulations. This study attempts to assess the performance of a simple (linear scaling and Delta Change method) and complex correction technique (Local intensity scaling, Power transformation and Distribution mapping) on CORDEX(Coordinated Regional Climate Downscaling Experiment)simulated precipitation series for the Thanjavur district. The performance at annual resolution is evaluated using various statistical parameters such as Correlation, Root Mean Square Error and Bias against the observed precipitation data. The raw RCM estimates were improved significantly after the bias correction with all methods. However, Power transformation exhibits good agreement with the observed data at the district level than other methods because it corrects both the mean and variance. The future climate was projected from 2021 to 2100 for RCP 4.5 and RCP 8.5 scenarios. The temporal distribution of future precipitation clearly shows that most of the years will receive heavy precipitation; rather, some years will receive low and average precipitation. The spatial distribution pattern indicates that the northeast monsoon will dominate over all the ranges and places. This study has provided clear information on future precipitation to the environmentalist, urban planners, and policymakers to take appropriate mitigation measures towards agriculture and disaster management. Rainwater harvesting, recharging the aquifers, afforestation, and redirecting the excess amount of water to the river through proper channels is the plausible actions suggested overcoming excessive precipitation in the future.

Analysing the bandwidths of hydrological change in small river catchments using an ensemble of high-resolution regional climate model projections

2021 ◽  
Author(s):  
Christoph Sauer ◽  
Peter Fröhle ◽  
Edgar Nehlsen ◽  
Diana Rechid ◽  
Laurens Bouwer ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Temporal Resolution ◽  
21St Century ◽  
Climate Model ◽  
Regional Climate ◽  
Small River ◽  
Precipitation Extremes ◽  
Climate Modelling ◽  
Simulated Precipitation ◽  
River Catchments

<p>Projections of the 21st century potential future climate evolution, especially for precipitation, are associated with high uncertainty and variability. Knowledge of the variability of the projected precipitation and resulting run-offs and the sources of uncertainties form the basis for analysis and assessment of future water-management options as well as potential risks related to droughts and flood events. The variabilities related to climate modelling can only be assessed by using a comparatively large number of climate projections.</p><p>In our research, we apply a large ensemble of regional climate model projections from the regional climate model REMO, driven by different global climate model simulations, at high temporal (hourly timestep) and high spatial (0.11 degree, or about 12.5 km) resolutions. Although the analysis of such big datasets involves considerable computational and storage capacities, this potentially helps to improve the simulation of future hydrological quantities in river catchments. For the analysis of the behaviour of small river catchments, we apply a semi-distributive hydrological model. Annual and winter average precipitation conditions show a robust and statistically significant increase especially for the RCP8.5 scenario. Precipitation ranges are compared with the ranges of runoff based on hydrological impact model runs driven by a set of simulated parameters from the regional climate model ensemble. The analyses are performed for a sub-catchment of the Lower Elbe system (Krückau catchment), which is a typical small basin (area < 200km<sup>2</sup>) close to the city of Hamburg in northern Germany. The model runs cover a long simulation period of 150 years (1950-2100) with a temporal resolution of 1 day. Short term model runs with a temporal resolution of 1 hour were carried out for annual and seasonal (summer/winter) maximum runoff derived from the long-term simulations.</p><p>Average annual runoff shows an increase of 0 to 10 % for the RCP2.6 ensemble and an increase of 0 to 20 % for the RCP8.5 ensemble at the end of the 21st century. Annual and winter average conditions (precipitation sums and average runoff) of the RCP8.5 ensemble show a robust increase across different ensemble simulations. Extreme events however show high variability and no conclusive and robust trend. Analysis shows a good relation between average values of precipitation and average runoff (MQ). Future development of simulated annual maximum runoffs shows only a weak relation with future simulated precipitation extremes. However, summer maximum runoffs tend to show a relation with summer precipitation extremes. The behaviour of winter runoffs might be explained by altered future conditions of snow aggregation and melt in combination with high soil moisture. With increasing average and extreme temperatures, snow fall, snow accumulation and concentrated runoff caused by snow melt in spring are less likely to occur.</p><p>One of the conclusions drawn is that especially for assessing extreme precipitation and its impacts on small hydrological catchments it is necessary to apply regional climate model projections with high spatial and temporal resolution where further improvement is expected by making use of the upcoming generation of climate simulations on convection permitting scale.</p>

Spatial distribution of precipitation annual cycles over South Africa in 10 CORDEX regional climate model present-day simulations

2015 ◽  
Vol 46 (5-6) ◽  
pp. 1799-1818 ◽  
Author(s):  
Alice Favre ◽  
Nathalie Philippon ◽  
Benjamin Pohl ◽  
Evangelia-Anna Kalognomou ◽  
Christopher Lennard ◽  
...  
Keyword(s):  
South Africa ◽  
Spatial Distribution ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Annual Cycles
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