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Tamil Nadu Agricultural University (2013)

Analysing climate projections uncertainty and its related impact on crop production over tamilnadu

RAJALAKSHMI.D

Titre : Analysing climate projections uncertainty and its related impact on crop production over tamilnadu

Auteur : RAJALAKSHMI.D

Université de soutenance : Tamil Nadu Agricultural University

Grade : Doctor of Philosophy (PhD) in Agricultural Meteorology and climatology 2013

Résumé
A study was carried out at Agro Climate Research Centre, Tamil Nadu Agricultural University, Coimbatore in the academic year 2010-2013 to analyse the uncertainty in climate projection over Tamilnadu for the 21st century and the impact of climate change on rice, groundnut and maize crop yields. The predictions were made with the high resolution PRECIS RCM driven by HadCM3Q ensembles (HQ0, HQ1, HQ3, HQ16) lateral boundary conditions (LBCs) and RegCM4 driven by ECHAM5 LBCs for 130 years (1971-2100). Six weather parameters viz., solar radiation, maximum temperature, minimum temperature, relative humidity, wind speed and rainfall were extracted from the outputs of these model predictions for analysing the uncertainity, testing the usability and studying the impact. The deviation in weather variables between 2091-2100 decade and the base years (1971-2000) were calculated for all grids of Tamilnadu for ascertaining the uncertainty. These deviations indicated that all model members projected no appreciable difference in relative humidity, wind speed and solar radiation. The temperature (maximum and minimum) however showed a definite increasing trend with 1.8 to 4.0ºC and 2.0 to 4.8ºC, respectively. A high uncertainty was exhibited by the model members for rainfall as they projected high negative and positive deviations (-379 to 854 mm). The seasonal and monthly deviations have the same tendency for uncertainty in which the rainfall was found to be influenced by monsoon periods. The decadal trend analysis revealed an increasing trend towards 21st century for maximum and minimum temperature while others had negligible differences across members. However, the RegCM4 outputs projected higher rainfall than other members. The statistical verification of prediction by members with CRU observation during the base period (1971-2000) indicated the usability of future projections from these RCMs and a note of caution is that the rainfall may require a bias correction. The future yield simulations by DSSAT for all the three crops showed a decreasingtrend for both control (without CO2 enrichment) and CO2 enriched conditions. The difference in yield between control and CO2 enrichment is wide and consistent for rice and groundnut. In case of maize, almost same level of yield was predicted. The CO2 enriched (±550 ppm) yields of rice and groundnut had some peaks during middle of 21st century and there after declined, probably because of more warming noticed in the outputs. The rice and groundnut yields are higher for RegCM4 projection compared to PRECIS ensemble outputs, while it was otherwise for maize.

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