Solar dimming over the tropical urban region of Hyderabad, India: Effect of increased cloudiness and increased anthropogenic aerosols

Abstract

[1] The present work examines the multidecadal changes in the net downward shortwave radiation (NDSWR) over the urban region of Hyderabad, India, during the period . The trends in NDSWR and in cloud optical depth (COD) are analyzed over the region using the Modern Era Retrospective-Analysis for Research and Applications (MERRA 2D), which is a newly available data set. The NDSWR exhibits a significant reduction of ∼−20.25 W m −2 for the period 1993-2005; however, it declined at a slower rate (0.468 W m −2 ) during the period 1979-1992. This reduction translates to −1.56 W m −2 yr −1 in the first period and to −0.04 W m −2 yr −1 in the second. The large difference in the NDSWR trends between the two periods is mainly attributed to the dramatic increase in high COD and in aerosol optical depth (AOD) during the last decade. The total COD over the region suggests an increase of 6.85% during the study period, with the larger increase to be depicted in the high-level clouds (70.86%). Furthermore, retrievals of AOD 550 from Microtops-II Sun photometer and Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) show a significant increase of ∼34% and ∼20% during the period 2002-2008 over Hyderabad, respectively. It is demonstrated that aerosols and clouds contribute to the remarkable reduction in NDSWR over Hyderabad in the recent years, thus resulting in a continuous solar dimming over the area. The main role in the decline of NDSWR has been the increase in COD of the high clouds, mainly in monsoon and premonsoon. On the other hand, the dramatic increase in the AOD 550 plays an important role in the decrease of NDSWR, mainly in winter. Furthermore, the indirect aerosol effect can modify the cloud formation, albedo, and lifetime, also playing a key role in the aerosol-cloud-radiation interactions.

Influence of land use/land cover (LULC) changes on atmospheric dynamics over the arid region of Rajasthan state, India

“…The system employs an incremental analysis update (IAU) procedure (Bloom et al, 1996) to eliminate the shocks that are otherwise associated with the observations. Satisfactory agreement between MERRA products and observations from ground-based instruments or satellites has been observed over India (Badarinath et al, 2010;Gautam et al, 2011).…”

Trend Analysis in Annual and Monthly Pan Evaporation and Pan Coefficient in the Context of Climate Change in Togo

“…Oguntunde et al [34] reported that Epan and solar radiation decreased significantly in all the months (p < 0.01) and the reduction ranged from 5.1% per decade in March to 9.3% per decade in August in Nigeria. Similarly Badarinath et al [35] found that the decline in solar radiation over Hyderabad in India was more intense during the period 1993-2005 compared to 1980s and attributed this to an increase in cloudiness mainly in monsoon. The Mann-Kendall test revealed increasing trend in monthly Epan except in March and June when Epan non-significantly decreased with year at Lome.…”

Aerosol Characteristics over the Indo-Gangetic Basin: Implications to Regional Climate

“…Such aerosols form thick layers of haze in winter, termed as Atmospheric Brown Clouds (ABC), which block the solar radiation reaching to the surface [101]. In [102], they have reported in their study over India that the AODs derived from TOMS data from 1979 to 2000 increased by ~11% per decade during the winter with large values over the IGB region, which consequently affect the surface reaching solar radiation, known as "solar dimming" [103][104][105]. The average solar dimming observed over India is about −0.86 W m −2 yr −1 , while during winter, pre-monsoon and monsoon seasons the same was observed to be about −0.94, −1.04 and −0.74 Wm −2 , respectively [104].…”