CORDEX South Asia Research Articles

Can offshore wind energy help to attain carbon neutrality amid climate change? A GIS-MCDM based analysis to unravel the facts using CORDEX-SA

Harnessing offshore wind energy helps to achieve carbon neutrality. However, the availability of wind resources is sensitive to climate change and also depends on the available foundation technologies of wind turbines. Investigating annual energy production (AEP) and CO2 equivalent emission avoidance using offshore wind farms helps to make appropriate energy strategies. This study uses an ensemble developed using CORDEX-South Asia regional climate models by assigning weights derived from the CRITIC multi-criteria technique to estimate AEP under two representative concentration pathways (RCP), i.e., RCP4.5 and RCP8.5 scenarios in the North Indian Ocean. To account for the impact of climate change, inter and intra-annual variations in the wind power density (WPD), capacity factor (CF), and AEP are estimated. Estimates based on the feasibility of foundation technology show that the cumulative AEP obtained from the 240 MW wind farm in historic, near- and far-future scenarios are 357.91 TWh, 808.6 TWh, and 4888.78 TWh, respectively. In the near future, harnessing offshore wind energy can reduce CO2 emissions by 4500 million tons annually. The findings of this study suggest that harnessing offshore wind energy by installing farms within the study area could help in the massive reduction of CO2 emissions leading to carbon neutrality.

Past and future changes toward earlier timing of streamflow over Pakistan from bias-corrected regional climate projections (1962–2099)

Pakistan has experienced seasonal changes of streamflow, causing a lack of available water resources for agriculture. However, understanding of future seasonal changes of streamflow over Pakistan remains limited. This study assessed the past and future changes in streamflow timing along the four major rivers of Pakistan (Upper Indus, Kabul, Jhelum, and Chenab River basins), using observational data and bias-corrected hydrological projections. Firstly, the VIC-river routing model was simulated forced by simulated daily surface and base runoff data from six CORDEX-South Asia regional climate models (1962–2099). Secondly, the minimum and seasonality bias in simulated daily streamflow data were corrected based on observational records. To quantify seasonal changes of the hydrologic regime, half of annual cumulative streamflows (HCSs) and center-of-volume dates (CVDs) were computed from observed and bias-corrected simulated streamflow data. Over 1962–2019, observational records showed a significant decreasing trend in CVD (that is, an earlier onset of the wet season) by a range between −4.5 and −12.6 days across the three river basins, except for Chenab River basin. Bias-corrected hydrologic projections showed decreased CVD across the four study river basins by −4.2 to −6.3 days during the record period (1962–2019). The decreased CVDs ranges from −5 to −20 days in the near future (the 2050–2059 average) and −11 days to −37 days in the far future (the 2090–2099 average). This study reported diverse hydrologic responses to a similar magnitude of near-surface temperature in Pakistan, highlighting a need to develop basin-specific water resources mamangement and policies for climate change adaptation.

Regional earth system model for CORDEX‐South Asia: A comparative assessment of RESM and ESM over the tropical Indian Ocean

AbstractUnderstanding climate variability requires good quality high resolution spatially and temporally varying ocean fields due to its decisive role in regulating the region's climate, including the Indian summer monsoon. In this regard, we employed a new high‐resolution regional earth system model (RESM), namely ROM over CORDEX South Asia. We demonstrated the performance of the RESM and its added value over the global earth system model, namely MPI‐ESM, in simulating the hydrographic characteristics and associated mechanism over the tropical Indian Ocean (TIO). ROM shows better skill than MPI‐ESM in simulating the near‐surface and subsurface characteristics of the ocean. However, larger added values are noticed for subsurface (>350 m) thermal structure. MPI‐ESM's cold sea surface temperature (SST) bias is reduced in ROM which is associated with weaker winds, anomalous cyclonic wind stress curl, enhanced stratifications, and a shallower mixed layer, resulting in greater upper‐ocean heating. The reduced SST bias is also consistent with improved ocean meridional heat transport (OMHT) in ROM. For example, reduced southward export of OMHT over the Arabian Sea increases the surface warming by ~4%, reducing the RMSE by ~0.2–0.6°C and becoming closer to observation. The anomalous cyclonic wind stress curl, in turn, caused mixed layer stratifications in the western Indian Ocean. The advective heat transfer from the south‐eastern Indian Ocean to the western Indian Ocean reduced oceanic cooling by vertical processes, overcame the cooling by the net loss of surface heat fluxes, and favoured the TIO's surface warming.

Regional earth system modelling framework for CORDEX-SA: an integrated model assessment for Indian summer monsoon rainfall

An effort is made to implement a regional earth system model (RESM); ROM, over CORDEX-South Asia (SA). The added value of RESM is assessed for mean precipitation, its variability (intraseasonal to interannual), extremes, and associated processes. In this regard, ROM’s fields are compared with the respective fields of its standalone version (REMO), the models belonging coupled model intercomparison project (CMIP5 and CMIP6), and regional climate models of CORDEX-CORE simulations. RESM shows substantial improvement for most of the Indian monsoon’s aspects; however, the magnitude of the value addition varies spatiotemporally and also with different aspects.. The improved representation of intraseasonal variability (active-break spell’s duration and intensity) and Interannual variability attributed to improved mean seasonal precipitation. Additionally, correct representation of sea surface temperature, Indian Ocean Dipole, and its underlying dynamics also contribute to improving the mean precipitation. The notable improvement is seen especially over the south-eastern regions of the Bay of Bengal (BoB) and South-Central India, where increasing (decreasing) low-pressure systems over Central India (BoB) are noticed as a consequence of air-sea coupling, leading to enhanced (reduced) precipitation over Central India (BoB), reducing dry (wet) bias found in REMO and the other models. Despite substantial improvements, RESM has a systematic wet bias in the mean precipitation associated with a warm bias over the western coast of the Arabian Sea. An overestimation of very high extreme precipitation due to the enhanced contribution of low-pressure systems indicates the model’s limitations, suggesting the need for further tuning of the RESM.

Impact of horizontal resolution on monsoon precipitation for CORDEX-South Asia: A regional earth system model assessment

For the first time for CORDEX-South Asia, a high-resolution regional earth system model (ROM) is adopted to assess the impact of horizontal resolution (0.22° and 0.11°) in simulating the Indian summer monsoon rainfall (ISMR) and the underlying spatiotemporal variability. ROM at both resolutions bears a close resemblance to observations in simulating the mean precipitation climatology compared to other regional climate models (RCMs) participated in CORDEX- South Asia. ROM shows substantial improvement relative to the ensemble mean of the RCMs included in CORDEX-South Asia. While comparing both simulations with observations, some systematic wet and dry bias over Central India (CI) and Northern Western Ghats is noticed. In general, the wet/dry bias over India is mainly associated with the overestimation/underestimation of the large-scale/convective component. Increasing horizontal resolution from 0.22° to 0.11° significantly adds value in simulating the JJAS mean precipitation by reducing the wet bias over western central India (WCI) and southern peninsular India and dry bias over eastern CI. The reduction in wet/dry bias is mainly associated with suppression/enhancement of the large scale/convective precipitation. This improvement in mean precipitation is partially due to the improved representation of the propagation of mesoscale systems such as boreal summer intraseasonal oscillation (eastward and northward). Despite the above improvements, the wet precipitation bias, particularly over WCI, persists. The weaker Findlater Jet associated with weaker land-ocean thermal contrast caused by the warm sea surface temperature (SST) bias over the western Arabian Sea (AS) suggests that AS moisture transport does not contribute to the wet bias over India. The wet bias is possibly associated with favourable atmospheric conditions (atmospheric instability).

Impact of climate change on hydrology components using CORDEX South Asia climate model in Wunna, Bharathpuzha, and Mahanadi, India.

Detecting the probable impact of climate change responses on hydrological components is most important for understanding such changes on water resources. The impact of climate change on virtual parameters of water was assessed through hydrological modeling of the Wunna, Mahanadi (Middle), and Bharathpuzha watersheds. In this article, future hydrological component responses under two Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios were considered for investigating the runoff, sediment, and water storage components. RegCM4 CSIRO-Mk3.6.0 CORDEX South Asia of RCM model was used which is specially downscaled for the Asian region by IITM-India. Delta change method was adopted to remove bias correction in RCM data. Hydrological simulation for current and future periods was performed by GIS interfaced Soil Water and Assessment Tool (SWAT) model. The surface runoff of Wunna and Bharathpuzha watersheds and the yield of sediment are expected to increase further under RCP8.5 than RCP4.5 and in contrast to Mahanadi watershed. Both blue water storage (BW) and green water storage (GWS) of Wunna watershed are expected to decline under RCP4.5, and rise under RCP8.5 scenario. Both BW and GWS of Bharathpuzha are expected to increase in the future except in western region under RCP4.5 scenario. BW of Mahanadi is expected to increase in the future. However, GWS will decrease in some of the sub-basins. The model-generated results will be helpful for future water resources planning and development.

Performance evaluation of CORDEX-South Asia simulations and future projections of northeast monsoon rainfall over south peninsular India

The northeast monsoon (October–December; NEM) rainfall is a very important entity to about 250 million people residing in the South Peninsular India (SPI) region as it is their principle rainy season and contributes mostly to their annual rainfall. The aim of the study is to obtain the future projections of NEM rainfall over this region representing three different greenhouse gas emission scenarios (i.e., RCP 2.6, RCP 4.5 and RCP 8.5) for two future time slices, i.e., near (2020–2049) and far future (2070–2099) estimated from a set of high-resolution regional climate simulations performed under CORDEX-SA experiments. To achieve that, first, an assessment of ten CORDEX-SA regional climate model (RCM) simulations is done for NEM rainfall over SPI for present climate (1976–2005) against India Meteorological Department high resolution (0.25o × 0.25o) gridded rainfall analysis dataset. Then, the change in NEM rainfall over SPI in the near and far future is computed after applying standardized reconstruction technique to adjust the bias present in the models. The results suggest that most of the CORDEX-SA experiments are able to simulate the spatial distribution of NEM seasonal rainfall and its variability over SPI but there is an inability in capturing realistic magnitudes and the errors are more over the east and west coast where most of the rainfall occurs. The experiment with RCA4 driven by EC-EARTH global model and REMO2009 driven by MPI-ESM has a fairly lesser bias than the other models, whereas the bias is more in LMDZ-IITM-RegCM4. The experiments by CCAM models have very similar characteristics in representing the rainfall pattern. The standardized reconstruction bias correction technique was found to significantly improve the performance of the climate models in representing the climatological mean and inter-annual variability of (IAV) of NEM rainfall over SPI, but in case of categorical rainfall years, improvement is seen only in the normal rainfall years. In the future, for RCP 2.6, there is a rise in NEM rainfall in the first half of the twenty-first century, which is projected to decline after that; however, in the other two scenarios, the rainfall is projected to increase. It is also found that there may be lesser excess rainfall years and more deficit rainfall years in the RCP 4.5 and 8.5 scenarios in the near future, and no deficit rainfall years are projected in the far future in both these scenarios based on the present climate. It is also noticed that the variability in the NEM rainfall over this region may remarkably increase in all the three future scenarios, which will highly impact various water resources management sectors. Thus, this study is very useful in determining the effects on various sectors due to the variability in NEM rainfall over this region and for adapting to climate change using advanced technologies for a sustainable future.

Future changes in growing degree days of wheat crop in Pakistan as simulated in CORDEX South Asia experiments

Climate change has become a global phenomenon having severe ramifications on socio-economic sectors such as agriculture, water resources, environment and health. The effects of changing climate are much more prominent on developing economies as compared to the implications on well-developed industrial powers. Pakistan is one of the struggling agricultural economies confronting the issues of food insecurity as a consequence of profound climatic conditions. Notable changes in climatic factors such as temperature can have a direct effect on Growing Degree Days (GDD) and may alter the growing season length (GSL). Growing season length is an important factor in ensuring that each crop developmental stage has a sufficient period for the transition to the next developmental stage. Lengthening or shortening of GSL can have dire threats to crop development and ultimately, production. This study has been conducted to assess the changes in GSL in response to the variability in daily maximum and minimum temperatures with a base temperature of 5°C across Northern, Central and Southern Pakistan. RCP 4.5 and 8.5 have shown an increase of 2°C and 5.4°C in minimum and maximum temperatures, respectively.

Investigation of seasonal droughts and related large-scale atmospheric dynamics over the Potwar Plateau of Pakistan

As a result of climate change and unsustainable land use management in the recent past, droughts have become one of the most devastating climatic hazards whose impacts may prolong from months to years. This study presents analysis of droughts for two major cropping seasons, i.e., Kharif (May–September) and Rabi (October–April), over the Potwar Plateau of Pakistan. The analysis is performed using various datasets viz. observational, reanalysis, and Regional Climate Models (RCMs), for the past (1981–2010) and future (2011–2100) time periods. The following two methods for the identification of dry and wet years, also referred to as drought and wetness, are applied: (1) the percentile rank approach and (2) the drought indices, Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI). Future projections of droughts are investigated using RCM (RegCM4.4 and RCA4) outputs from CORDEX South Asia domain under two Representative Concentration Pathway (RCP) scenarios, RCP4.5 and RCP8.5. Generally, the indices show non-significant decreasing trends of drought severity in the recent past for all cases; however, significant increasing trends are observed for annual (0.006) and Kharif (0.007) cases under RCP4.5 scenario. The analysis of large-scale atmospheric dynamics suggests the significant role of low-level geopotential height anomalies over Tibetan Plateau (northwest of Pakistan) during Kharif (Rabi) season in controlling drought occurrence by transporting moisture from the Bay of Bengal (Arabian Sea). Moreover, composites of vertically integrated moisture transport, moisture flux convergence/divergence, and precipitable water anomalies show their marked contribution in maintaining the drought/wetness conditions over the Potwar region.

Future projection of winter precipitation over northwest India and associated regions using CORDEX-SA experiments

Precipitation during winter months of December, January, and February over northwest India is important for the production of winter crops as well as for glacial accumulation which goes on to feed major rivers in India with fresh water supply. Winter precipitation over this region is due to the movement of synoptic systems approaching from the Mediterranean known as Western Disturbances (WDs). So far, spatial pattern of winter precipitation over this region has not been studied using different RCMs. The present study evaluates the regional climate model employed in Coordinated Regional Climate Downscaling Experiment in South Asia (CORDEX-South Asia) framework to characterize winter precipitation over northwest India and Karakoram region. There are 16 CORDEX-South Asia experiments with 3 regional climate models (RCM) driven with 16 global climate models (GCM). Precipitation climatology is calculated for different RCM along with their ensemble. All the experiments show a wet bias over the region. The selection of best performing RCM is identified using various statistical analyses. The CORDEX experiment run by EC_EARTH RCM with RCA4 GCM developed by Swedish Meteorological and Hydrological Institute (SMHI) is identified as the best performing model when compared with observation. The change in future seasonal mean precipitation is assessed over northwest India and Karakoram region under two representation concentration pathways (RCP4.5 and RCP8.5) scenarios. A positive change in precipitation is observed over Karakoram region under the two RCP scenarios for near future and far future periods. The magnitude of precipitation change is found to be less over the study area under RCP 8.5 scenario for near future period compared to other scenario and time period.

Application of hydrological model for assessment of water security using multi-model ensemble of CORDEX-South Asia experiments in a semi-arid river basin of India

This study analyses the impacts of climate change on water resources in the Banas River Basin, which is located in a semi-arid part of the state of Rajasthan in India. A bias-corrected ensemble mean of three CORDEX-SA driving GCM experiments (CNRM-CM5, CCSM4, and MPI-ESM-LR) was used with the Soil Water Assessment Tool (SWAT) to predict water yield and evapotranspiration for three future periods (2011–2040, 2041–2070, and 2071–2099) under two representative concentration pathway scenarios (RCP4.5 and RCP8.5), and the results were compared with the data of a historical period (1979–2008). The SUFI-2 method was used for the calibration and validation of the SWAT model. The model was calibrated for the period of five years (1982–1986) and validated for the next five years (1987–1991). The values of R2, NSE, bR2, PBIAS, and RSR were, respectively, 0.78, 0.77, 0.61, 47.4 and 0.48 during the calibration period, and 0.71, 0.65, 0.60, 72.1 and 0.59 during the validation period. Trend analysis was also performed for annual future predicted flows using the Sen Slope method. From the results, it can be predicted that precipitation, evapotranspiration, and water yield will increase in all the three future periods under both RCP4.5 and RCP8.5. Water availability in the future in the basin (zone wise) was identified using appropriate indicators. Per-capita water availability and meteorological variation were used to calculate future water availability and, considering these indicators, it can be concluded that zone 3 will better than the other zones. Zone 3 exhibits high values of per capita water availability and meteorological variation. This study will be useful in understanding the impacts of climate change on the water availability of the river basin and may help in overall water management in the present and the future.

Climatic and hydrological projections to changing climate under CORDEX-South Asia experiments over the Karakoram-Hindukush-Himalayan water towers

The complex snow and glacier (cryosphere) dynamics over the “third pole” mountainous regions of the Karakoram-Hindukush-Himalayas (HKH) makes this region challenging for accurate hydrological predictions. The objective of this study is to investigate the impacts of climate change on major hydrological components (precipitation-runoff, snow- and glacier-runoff, evapotranspiration and inter-annual change in streamflows) over the Hunza-, Gilgit- and Astore-River basins, located in HKH. For this purpose, three different hydrological models (snowmelt runoff (SRM), HEC-HMS and HBV are tested over snow- and glacier-covered river basins. These are subsequently integrated with the climate projections simulated from regional climate models (RCMs) developed under CORDEX-SA experiments. The basin-wide RCM-simulations for future scenarios exhibited an increase in precipitation but decline in intensity of rise over high-altitude zones. The temperature rise showed a maximum increase during monsoon by 4.18 °C, 4.37 °C and 4.34 °C over Hunza-, Gilgit- and Astore-River basins, respectively, for the period 2071–2099 (2090s) and a high emission scenario (RCP8.5). Further, in response to rise in precipitation and temperature, the SRM simulations showed a significant increase in snow- glacier-melt runoff (49%, 42% and 46% for SRM) and precipitation runoff (23.8%, 15.7% and 27% for HEC-HMS) in the Hunza-, Gilgit- and Astore-River basins, respectively, for the 2090s under RCP8.5. The streamflow projections for SRM showed a shift in hydrological regime with an increase by 369 (168.4%), 216.5 (74.8%) and 131.8 m3/s (82%) during pre-monsoon in the Hunza-, Gilgit- and Astore-River basins, respectively and then decline by −73.2 m3/s (−13.9%) and −45.4 m3/s (23.4%) during monsoon of the 2090s, in the Hunza- and Astore-River basins, respectively, under RCP8.5. Overall, the projections show that the pre-monsoon and monsoon seasons are expected to be strongly influenced by climate change, through alterations in snow- and glacier-accumulation, and melt regimes with substantial consequences for river runoff in the region.

Shift in Potential Malaria Transmission Areas in India, Using the Fuzzy-Based Climate Suitability Malaria Transmission (FCSMT) Model under Changing Climatic Conditions.

The future implications of climate change on malaria transmission at the global level have already been reported, however such evidences are scarce and limited in India. Here our study aims to assess, identify and map the potential effects of climate change on Plasmodium vivax (Pv) and Plasmodium falciparum (Pf) malaria transmission in India. A Fuzzy-based Climate Suitability Malaria Transmission (FCSMT) model under the GIS environment was generated using Temperature and Relative Humidity data, extracted from CORDEX South Asia for Baseline (1976–2005) and RCP 4.5 scenario for future projection by the 2030s (2021–2040). National malaria data were used at the model analysis stage. Model outcomes suggest that climate change may significantly increase the spatial spread of Pv and Pf malaria with a numerical increase in the transmission window’s (TW) months, and a shift in the months of transmission. Some areas of the western Himalayan states are likely to have new foci of Pv malaria transmission. Interior parts of some southern and eastern states are likely to become more suitable for Pf malaria transmission. Study has also identified the regions with a reduction in transmission months by the 2030s, leading to unstable malaria, and having the potential for malaria outbreaks.

Assessment of climatological tropical cyclone activity over the north Indian Ocean in the CORDEX-South Asia regional climate models

This study evaluates the ability of the regional climate models (RCMs) in the Coordinated Regional Climate Downscaling Experiment for South Asia (CORDEX-SA) to simulate the tropical cyclone activity in the north Indian Ocean. The RCMs used in the CORDEX-SA are Rossby Centre regional atmospheric model version 4 (RCA4) and Regional Climatic Model version 4 (RegCM4) forced by the ECMWF Interim Reanalysis (ERA-Interim) from 1989 to 2008. Both models have reasonable skill in capturing the observed climatological seasonal and spatial distribution of the genesis and track of the tropical cyclones. However, the two issues faced are (i) in RegCM4 model, higher number of tropical cyclones throughout the year compared to observations in addition to the unrealistic simulation of tropical cyclones during winter and (ii) in the RCA4 model, relatively higher tropical cyclone activity over the Arabian Sea compared to the Bay of Bengal. In the RCA4, the anomalous large-scale lower tropospheric cyclonic circulation observed over the southern Arabian Sea might be responsible for the overestimation in the number of tropical cyclones over there. In both models, the relationship between minimum pressure and the maximum wind is well simulated even though there is an underestimation in the intensity of the tropical cyclones. Quantitative analysis of large-scale environmental parameters that influence the tropical cyclone activity using an index called genesis potential index showed that in the RegCM4 model, the model simulates seasonal variation (enhancement/suppression) of environmental conditions fairly good as seen in the observation. However, the model has higher number of tropical cyclones in all the seasons, which is due to the enhanced large scale dynamical and thermodynamical parameters. The cold and wet bias in the middle troposphere causes the reduction in the mid-layer saturation deficit throughout the year, which in turn favours an unrealistic high number of tropical cyclone genesis. Therefore, the changes in the large scale dynamics and relatively saturated middle troposphere in the model might be responsible for the higher number of tropical cyclones.

Obtaining best parameterization scheme of RegCM 4.4 for aerosols and chemistry simulations over the CORDEX South Asia

The regional climate model RegCM 4.4 at 50 km resolution is used to conduct a sensitivity study over South Asia Coordinated Regional climate Downscaling Experiment domain during the period 1998–2002, in order to investigate the best cumulus convective precipitation scheme, planetary boundary layer (PBL) and land-surface scheme. The inferences obtained from 11 sensitivity experiments include the better performance of community land model version 4.5 (CLM 4.5) over biosphere–atmosphere transfer scheme, Tiedtke as cumulus convective precipitation scheme and University of Washington (UW) as PBL scheme. The simulation with these parameterization schemes well captures the monsoon precipitation pattern over India ~ 7 mm/day and North Eastern Region of India (NER) ~ 12 mm/day, which are comparable to observations with a significant correlation of R2 > 0.93. The observed temperatures are also well simulated by the model. Therefore, RegCM 4.4 with these parameterization schemes is further used to simulate the aerosol fields (aerosol optical depth, AOD and black carbon, BC) and aerosol direct radiative forcing (DRF) for the period 2011–2014 over the same domain with special emphasis on NER. The model captures the seasonality in AOD and BC over the Indian Subcontinent and NER. BC hotspots in the Indo-Gangetic Plain and China are well captured by the model. The observed to simulated BC ratio over Dibrugarh (located in NER) is found to be improved. The model underestimation is significant in the dry season when burning over the region is predominant, which has not been considered by the emission inventories properly. Simulated DRF is found to exhibit seasonality qualitatively as well as a North–South latitudinal gradient.

Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan

The high mountains of Hindu-Kush Karakoram and Himalaya (HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km 2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data ( r =0.88). Local temperature lapse rate of 0.0075 °C/m is used. 2 °C critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration (0.86% and 0.90%) and validation (0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios. Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.

Climate conditions and drought assessment with the Palmer Drought Severity Index in Iran: evaluation of CORDEX South Asia climate projections (2070–2099)

Climate change projections were evaluated over both the whole Iran and six zones having different precipitation regimes considering the CORDEX South Asia dataset, for assessing space–time distribution of drought occurrences in the future period 2070–2099 under RCP4.5 scenario. Initially, the performances of eight available CORDEX South Asia Regional Climate Models (RCMs) were assessed for the baseline period 1970–2005 through the GPCC v.7 precipitation dataset and the CFSR temperature dataset, which were previously selected as the most reliable within a set of five global datasets compared to 41 available synoptic stations. Though the CCLM RCM driven by the MPI-ESM-LR General Circulation Model is in general the most suitable for temperature and, together with the REMO 2009 RCM also driven by MPI-ESM-LR, for precipitation, their performances do not overwhelm other models for every season and zone in which Iranian territory was divided according to a principal component analysis approach. Hence, a weighting approach was tested and adopted to take into account useful information from every RCM in each of the six zones. The models resulting more reliable compared to current climate show a strong precipitation decrease. Weighted average predicts an overall yearly precipitation decrease of about 20%. Temperature projections provide a mean annual increase of 2.4 °C. Future drought scenarios were depicted by means of the self-calibrating version of the Palmer drought severity index (SC-PDSI) model. Weighted average predicts a sharp drying that can be configured as a real shift in mean climate conditions, drastically affecting water resources of the country.

Statistically downscaled projections of CORDEX South Asia using quantile mapping approach over Pakistan region

Statistically downscaled projections of CORDEX South Asia using quantile mapping approach over Pakistan region

Statistically downscaled projections of CORDEX South Asia using quantile mapping approach over Pakistan region

Apprehending regional scale climate information from global scale climate models brings uncertainties primarily due to insufficient incorporation of climate information at local scale. We implemented the quantile mapping (QM) approach based on in-situ data that removed the systematic biases in the regional scale simulations of the CORDEX South Asia data for maximum temperature, minimum temperature and precipitation that covers the Pakistani domain. Post processed results were modelled into probability density functions (PDFs) to identify climate change shifts in various statistical moments. The PDF-based analysis for temperature reported negatively skewed patterns in distributions for projections as compared to baseline which forced shifting of percentiles and means towards extreme magnitude regimes. The PDF-based analysis for precipitation displayed lower kurtotic values with fatter and lengthier tails in the projections as compared to baseline which suggested higher frequencies of precipitation extremes to occur in the times to come.

Assessment of CORDEX-South Asia experiments for monsoonal precipitation over Himalayan region for future climate

Precipitation is one of the important climatic indicators in the global climate system. Probable changes in monsoonal (June, July, August and September; hereafter JJAS) mean precipitation in the Himalayan region for three different greenhouse gas emission scenarios (i.e. representative concentration pathways or RCPs) and two future time slices (near and far) are estimated from a set of regional climate simulations performed under Coordinated Regional Climate Downscaling Experiment-South Asia (CORDEX-SA) project. For each of the CORDEX-SA simulations and their ensemble, projections of near future (2020–2049) and far future (2070–2099) precipitation climatology with respect to corresponding present climate (1970–2005) over Himalayan region are presented. The variability existing over each of the future time slices is compared with the present climate variability to determine the future changes in inter annual fluctuations of monsoonal mean precipitation. The long-term (1970–2099) trend (mm/day/year) of monsoonal mean precipitation spatially distributed as well as averaged over Himalayan region is analyzed to detect any change across twenty-first century as well as to assess model uncertainty in simulating the precipitation changes over this period. The altitudinal distribution of difference in trend of future precipitation from present climate existing over each of the time slices is also studied to understand any elevation dependency of change in precipitation pattern. Except for a part of the Hindu-Kush area in western Himalayan region which shows drier condition, the CORDEX-SA experiments project in general wetter/drier conditions in near future for western/eastern Himalayan region, a scenario which gets further intensified in far future. Although, a gradually increasing precipitation trend is seen throughout the twenty-first century in carbon intensive scenarios, the distribution of trend with elevation presents a very complex picture with lower elevations showing a greater trend in far-future under RCP8.5 when compared with higher elevations.