AIRS observations of seasonal variability in meridional temperature gradient over Indian region at 100 hPa

Journal of Earth system science

V Panwar2 3¹  S K Dash5²  R Bhatnagar1³  A Gupta1 2³  S K Dhaka1³  Savita M Datta4⁴  V Kumar1 2³ 

[1] Department of Physics and Astrophysics, University of Delhi, New Delhi 110 007, India.$$;Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi 110 061, India.$$;Department of Physics, Rajdhani College, University of Delhi, New Delhi 110 015, India.$$;Maitreyi College, University of Delhi, New Delhi 110 021, India.$$

关键词: Meridional temperature gradient;    Atmospheric Infra Red Sounder (AIRS) data;    Indian summer monsoon;    outgoing long-wave radiation (OLR).;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

To investigate the temperature changes at 100 hPa over Indian region from Arabian Sea (AS) to Bay of Bengal (BOB), analysis is performed using Atmospheric Infra Red Sounder (AIRS) temperature and outgoing long-wave radiation (OLR) data of 9 years (2003–2011). Fine-scale temperature variations have been studied and shown for summer (March–April–May, MAM), summer monsoon (June–July–August–September, JJAS) and winter (November–December–January–February, NDJF) months. Similarities and differences in the latitudinal and longitudinal variation of temperature and the possible causes have been examined. During MAM and NDJF, the temperature increases latitudinally by ∼2–3 K and ∼4–5 K from 3.5° to 20.5°N, respectively. However, the temperature decreases by ∼2.0–2.5 K during JJAS. A similar contrasting behaviour is observed in latitudinal temperature gradient. For MAM and NDJF, the gradient decreases from ∼0.18 to ∼0.14 K/deg and ∼0.25 to ∼0.18 K/deg, respectively, as we move longitudinally from 60° to 90°E; however, for JJAS, it increases from ∼0.10 to ∼0.14 K/deg over the same longitudes. It is found that latitudinal temperature gradient for NDJF is larger by about a factor of 1.5. Analysis suggests latitudinal change in temperature occurs due to low OLR (proxy of convection) and its northward progression during summer monsoon. Correlation coefficient (𝑅xy) between OLR and temperature is computed latitudinally (3.5° to 20.5°N) at different longitudes and during JJAS (monsoon months), 𝑅xy is negative (∼−0.73) over 60° and 70°E longitudes, but it turns positive (∼0.92) over 80° and 90°E longitudes (which is convectively active region), suggesting a close association between low temperature and low OLR. Land–sea contrast is also observed in temperature at 100 hPa with a slight increase (∼0.5 K) from sea to land.

【 授权许可】

Unknown