The hydroclimatic intensity index (HY‐INT) is a single index that quantitatively combines measures of precipitation intensity and dry spell length, thus providing an integrated response of the hydrological cycle to global warming. The HY‐INT index is a product of the precipitation intensity (PINT, intensity during wet days) and dry spell length (DSL). Using the observed gridded rainfall data sets of 1951–2010 period, the changes in HY‐INT, PINT, and DSL over the Indian monsoon region have been examined in addition to changes in maximum consecutive dry days (MCD). We have also considered 10 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models for examining the changes in these indices during the present‐day and future climate change scenarios. For climate change projections, the Representative Concentration Pathway (RCP) 4.5 scenario was considered. The analysis of observational data during the period 1951–2010 suggested an increase in DSL and MCD over most of central India. Further, statistically significant (95% level) increase in HY‐INT is also noted during the period of 1951–2010, which is mainly caused due to significant increase in precipitation intensity. The CMIP5 model projections of future climate also suggest a statistically significant increase in HY‐INT over the Indian region. Out of the 10 models considered, seven models suggest a consistent increase in HY‐INT during the period of 2010–2100 under the RCP4.5 scenario. However, the projected increase in HY‐INT is mainly due to increase in the precipitation intensity, while dry spell length (DSL) showed little changes in the future climate.

Abstract The central aim of this work is to investigate the characteristics of fog events over the United Arab Emirates (UAE) and identify the underlying physical processes responsible for fog initiation and dissipation. To achieve this, hourly meteorological measurements at eight airport stations, along with ERA5 reanalysis data (1995–2018), are utilized. The analysis indicates the dominance of radiation fog (RAD) as, on average, 70% of the observed events fall under this category. Fog in the UAE typically forms between 2000 and 0200 local time (LT) and dissipates between 0600 and 0900 LT. During a typical dense fog event recorded during 22–23 December 2017, cooling and moistening tendencies of up to 1.2 K h−1 and 0.7 g kg−1 h−1 are observed ~5–6 h before fog onset. In the vertical, a dry and warm layer above 750 hPa gradually descends from above 500 hPa to promote the development of fog. Similar conclusions are reached when analyzing composites of fog events. Further, the variability of fog occurrence associated with El Niño–Southern Oscillation (ENSO) patterns is explored. It is concluded that the El Niño (warm) and La Niña (cold) phases exhibit very different spatial characteristics with respect to surface meteorological variables. In particular, during El Niño events, the near-surface atmosphere is cooler and moister compared to La Niña events, favoring RAD fog formation over the UAE. Besides, fog events during El Niño years tend to last longer compared to La Niña years due to an earlier onset.

The differences in the vertical structure of mean wind and its diurnal variation from the surface to upper troposphere between wet and dry spells are studied using a unique data set consisting of surface and remote sensing (SOund Detection and Ranging and wind profilers) measurements made at Gadanki (13.5°N 79.2°E). Special emphasis was given to study the variation of low‐level jet (LLJ) and tropical easterly jet (TEJ), two most conspicuous features of the Indian summer monsoon. Largest and significant wind differences between the spells are observed in the lower troposphere (<4 km) with stronger winds during the dry spell than during wet spell. The spatial variation of LLJ and TEJ depicts intriguing differences between the spells. The LLJ splits into two branches over the Arabian Sea during the dry spell, while only one branch is apparent during the wet spell. On the 100 hPa level, the longitudinal extent of the TEJ is larger during the dry spell than during wet spell. The vertical variation (in particular, in the lower troposphere) of the amplitude and phase of diurnal cycle is significant and, to some extent, different during the dry and wet spells. The plausible mechanisms responsible for the change in the phase of the diurnal cycle with altitude are discussed. The amplitude of the diurnal cycle increases with altitude up to 2 km and then decreases. Largest amplitudes in the entire troposphere and lower stratosphere are found in the height region of 1–2 km. Given that LLJ peak magnitude and height exhibit a strong diurnal variation, one should be careful in obtaining characteristics of the LLJ and nocturnal LLJ from observations made at a fixed time. The diurnal variation of LLJ and TEJ exhibits distinct spatial variability in both spells. The results are compared and contrasted with earlier reports on intraseasonal variability of the LLJ and TEJ.