The impact of modified fractional conversion parameter (from cloud condensate to precipitation) in the revised simplified Arakawa‐Schubert (RSAS) convection scheme in Climate Forecast System version 2 on the simulation of Indian summer monsoon (ISM) is examined. While the default fractional conversion parameter is constant in RSAS, the modified parameter has the form of an exponential function of temperature above the freezing level, whereas below the freezing, level it is kept constant. The model simulation indicates RSAS with modified conversion parameter (RSAS_mod) shows a better fidelity in capturing the mean monsoon features over the ISM region. The spatial distribution of precipitation shows notable improvement over the ISM region. Most of the global general circulation models has a tendency to grossly overestimate (underestimate) the convective (large‐scale) rainfall over the ISM region, which has improved in RSAS_mod simulation. It is suggested that reduced rate of conversion of cloud condensate to convective precipitation above the freezing level leads to suppression of convective precipitation, which further increases the detrained moisture from the upper‐level, resulting enhancement in large‐scale precipitation. In addition to mean summer monsoon, the RSAS_mod indicates its potential in predicting an extreme rainfall event over Mumbai in high‐resolution global forecast system at T1534 horizontal resolution. (Ganai, M., Krishna, R. P. M., Tirkey, S., Mukhopadhyay, P., Mahakur, M., & Han, J.‐Y. Journal of Geophysical Research:Atmospheres, May, 2019 124. https://doi.org/10.1029/2019JD030278, 1-21)Read More
The CMIP5 models suggest an increase of about two heat waves and increase of 12–18 days in heat wave duration during the period 2020–2064. The spatial trend analysis of Heat Wave frequency (HWF) and Heat wave Duration (HWD) suggested that both the HWF and HWD will increase significantly over central and northwest India by 0.5 events per decade and 4–7 days per decade respectively. In the future climate change scenario, southern parts of India and coastal part of India which are presently unaffected by heat waves, are likely to be affected by heat waves. The study also suggests that the future increase in heat waves is caused due to strengthening of mid-tropospheric high and associated subsidence over central and northwest India. Land surface processes like depletion of soil moisture and increased sensible heat fluxes are also responsible for the increase in heat waves. The CMIP5 models also suggest that El Nino Modoki events may be responsible for the prolonged and more frequent future heat waves over India in the future climate scenario. (Rohini P., Rajeevan M., Mukhopadhay P., Climate Dynamics, online, March 2019, DOI:10.1007/s00382-019-04700-9, 1-14)Read More
Inter-annual variability of the dates of Indian summer Monsoon Onset over Kerala (MOK) is examined for the period 1971 to 2018. The mean date of MOK is observed as 2 June, however, the standard deviation of the present series is found to be less than that of the earlier IMD series. The MOK date series exhibit a large inter-annual variation during the study period with a dominant decadal periodic variation, significant at 10% level. The decadal mean values of monsoon onset exhibit a cyclic variation, and the 5 decades show characteristics of slightly delayed-normal-slightly delayed-normal-slightly delayed occurrence of monsoon onset in mean. The study has brought out the features of the short-term climatic changes in the time of occurrence of MOK which further shall be useful for making improvement in the present onset prediction models for better results. (Ghanekar S.P., Bansod S.D., Narkhedkar S.G., Kulkarni Ashwini, Theoretical and Applied Climatology, online, April 2019, DOI:10.1007/s00704-019-02853-5, 1-14)Read More
This study show that Dense fog occurred at IGI Airport, New Delhi during 2011-2016, causing a total economic loss of approximately 3.9 million USD (248 million Indian rupees) to the airlines. The analysis further found that from 2014-2015 onwards, there has been a reduction in the number of flight delays, diversions, and cancellations by approximately 88%, 55%, and 36%, respectively, due to the strict implementation of guidelines to facilitate the Category (CAT)-III landing for aircraft during dense fog.
Figure: Total economic losses due to dense fog which occurred at IGI Airport between 2011 and 2016. Black bar shows the total number of flights affected, red bar shows the economic loss (in millions USD), and blue line shows the total number of dense fog hours for visibility less than 200 m
(Kulkarni R., Jenamani R.K., Pithani P., Konwar M., Nigam N., Ghude S.D. Atmosphere, 10:198, April 2019, DOI:10.3390/atmos10040198, 1-10)
Observations for recent decades, post 1960, exhibit declining trend in monsoon rainfall with frequent occurrence and intensification of droughts along with an increase in percentage of area under moderate and severe drought conditions, in association with variations in sea surface temperature (SST) (Preethi B., Ramya R., Patwardhan S.K., Mujumdar M., Kripalani R.H., Climate Dynamics, online, April 2019, DOI:10.1007/s00382-019-04752-x, 1-26)Read More