Mansi JANMAIJAYA, Department of Geography, K.G.K. (P.G.) College, Moradabad, Uttar Pradesh , India
S.k. DHAKA, Department of Physics, Rajdhani College, University of Delhi, India
The effect of aerosols on earth’s radiation budget has proved most challenging to ascertain. Tropospheric aerosols may either result in net increase or decrease of temperature. The association between aerosols and temperature anomalies (surface and tropospheric temperature) for National Capital Region of India has been analyzed for four seasons, pre-monsoon, monsoon, post-monsoon and winter during 2003-15. The anomalies have been calculated as monthly deviations from the longer-term mean (here, the average monthly temperature for the period 2003-15). The present study is based on MODIS 3×3 aerosol product. The high-resolution data enables the analysis and characterization of aerosols, particularly at the local level. The tropospheric temperature (at 3 pressure levels i.e. 1000, 925 and 850 hPa) and surface air temperature is obtained from Atmospheric InfraRed Sounder (AIRS). The study has utilized level 3 monthly data product, which is geolocated, calibrated and cloud corrected radiances. The data is available at a spatial resolution of 1° × 1 ° (latitude × longitude).
Temperature anomalies and aerosols are inversely related, particularly in the pre-monsoon and winter season. The average surface air temperature has increased by approximately 1°C in the pre-monsoon season. On comparison with monthly averaged Aerosol Optical Depth (AOD), it was evident that the years with significant negative anomalies (>2 °C) were also years with high AOD. The temperature is declining in the winter season. It varies from around 0.12 °C at 1000 hPa, 1°C at 925 hPa to 0.5 °C at 850 hPa. The decreasing winter temperature can be attributable to the high concentration of aerosols. The subdued atmospheric circulation in the season, extends the lifetime of aerosols in the atmosphere. This points to cooling effect of aerosols on temperature. Aerosols thus, plays an important role in temperature variability in the region.
Keywords: Temperature Anomalies|Aerosols|AIRS|MODIS|National Capital Region