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

• Published in: Journal of Earth System Science Vol. 122; no. 1; pp. 201 - 213
• Main Authors: GUPTA, A, DHAKA, S K, PANWAR, V, BHATNAGAR, R, KUMAR, V, DATTA, SAVITA M, DASH, S K
• Format: Journal Article
• Language: English
• Published: India Springer-Verlag 01.02.2013; Springer Nature B.V
• Subjects: Auroral kilometric radiation; Climate; Convection; Correlation coefficient; Correlation coefficients; Earth and Environmental Science; Earth Sciences; Long wave radiation; Low temperature; Monsoons; Outgoing long-wave radiation; Seasonal variability; Seasonal variation; Seasonal variations; Seasons; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Summer; Summer monsoon; Temperature; Temperature changes; Temperature gradients; Temperature rise; Temperature variations; Wind; India; outgoing long-wave radiation (OLR); Meridional temperature gradient; Indian summer monsoon; Atmospheric Infra Red Sounder (AIRS) data
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-012-0254-y

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 ( R xy ) between OLR and temperature is computed latitudinally (3.5° to 20.5°N) at different longitudes and during JJAS (monsoon months), R xy 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.