**Author details**

**5. Conclusions**

188 Aerosols - Science and Case Studies

contributing factors.

lows:

MODIS satellite retrievals were used to investigate the spatiotemporal variations of MODIS retrieved aerosol and cloud products over Western Himalayan and Deccan Plateau regions. The data were also employed to study aerosol–cloud interaction and to quantify AIE over these regions for fixed LWP bins. The major conclusions of the present study are as fol‐

**•** The analysis of MODIS retrieved aerosol and cloud products, the interrelation between cloud between aerosol parameters and the estimation of the AIE reveal that the aerosol– cloud relationship as well as AIE changes magnitude and sign both with space and time (season). The change in the atmospheric circulation patterns, in‐flux/out‐flux of different types of aerosols and varying prevalent meteorological conditions may be the reason behind this positive/negative aerosol indirect effect. Analysis of MODIS retrievals further revealed that the aerosols can change microphysical properties of clouds. However, it is evident that such changes are not determined by aerosols alone as there may be several

**•** At all the stations, during 2000–2010, the sign of AE‐AOD correlation exhibited spatio‐ temporal variability. During winter, AE was positively correlated with AOD while during monsoon the correlation was negative with 95% of significance level at all the stations. In pre‐monsoon, the majority of the stations (78%) showed inverse AE‐AOD relationship, out of which about 86% of the correlations were significant at 95% confidence level. The changeover in the sign of AE‐AOD correlation may be attributed to the hygroscopic growth of the aerosol particles producing a significant shift in aerosol size spectrum which in turn

**•** Monthly variation of AOD and LWP for the study period and their seasonal correlation analysis points out that the sign of correlation (negative/positive) changes from season to season and place to place indicating spatiotemporal variability in these correlations. Reduction in LWP with AOD during winter, pre‐monsoon, monsoon, and post‐monsoon seasons may be attributed to the warming of the clouds due to the dust aerosols. Dust aerosols absorb the incoming solar radiation resulting into increase in cloud layer temperature, thereby enhancing evaporation of cloud droplets leading to the reduction of

**•** Estimated values of AIE showed that the average values of AIE during 2000–2010, at each category (CAT‐H, CAT‐M, and CAT‐L) were ‐0.04 ± 0.14, 0.01 ± 0.07, and 0.10 ± 0.48, respectively. About 57–71% of LWP bins revealed negative AIE at each category. During winter, prominent anti‐Twomey effect (with 25–80% of significance level) was observed in all the three categories. In pre‐monsoon, 86% (at CAT‐H) and 60% (at CAT‐M) of LWP bins showed positive AIE while about 71% (at CAT‐L) of LWP bins exhibited negative AIE

can substantially influence the magnitude of the AE.

LWP, i.e., the so‐called semi‐direct effect.

values.

Sandeep R. Varpe1,3, Gajanan R. Aher1\*, Amol R. Kolhe1,2 and Sanjay D. More4

\*Address all correspondence to: aher.g.r@gmail.com

1 Physics Department, Nowrosjee Wadia College, Pune, India

2 Department of Physics, Savitribai Phule Pune University, Pune, India

3 International Institute of Information Technology, Hinjewadi, Pune, India

4 Department of Atmospheric and Space Sciences, University of Pune, Pune, India

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