Behaviour of recurving cyclonic storms in Arabian Sea as a response to atmospheric interactions

During the year 1998, Arabian sea witnessed two distinct and unusual cyc\onic systems. The very severe cyclonic storm of June 1998 was the most severe storm since last fifteen years as far as Arabian Sea systems are concerned; while October 1998 system was unique for, Its unusual and sudden easterly track after almost touching Saudi Arabia coast, (ii) Very high speed of movement and (iii) Interaction and merger with another vortex present in Arabian Sea off Saurashtra coast. This study is an attempt to understand the peculiar behaviour of the systems in Arabian sea which do not intensify beyond cyclone stage or even show a tendency to weaken before crossing coast as a response to atmospheric interactions. All the cyclonic systems in Arabian Sea since 1975 (Satellite era) have been examined in detail and the main findings of the study are : (i) Interaction between cyclonic disturbances of different intensities simultaneously present, appears to be the key factor in determining the further intensification or not of the systems. (ii) Track prediction for the systems upto marginal cyclone stage appears to be governed mainly by middle level atmospheric forcing. (iii) Upper level wind steering is found to be important for movement of systems from severe cyclonic storm stage onwards. The above results have direct relevance to operational cyclone forecasting.

The implications of the recently recognized mid-20th century shift in the Earth system

Satellite observations offering detailed records of global environmental change are only available from 1979. Emerging studies combining high-quality instrumental and natural observations highlight that the Earth system experienced a substantial shift across the mid-20th century, one that appears to have taken place before the Great Acceleration of human activities from the 1950s. These new results have far-reaching implications for understanding ice-ocean-atmospheric interactions in the Anthropocene and highlight the urgent need for drastic cuts in carbon emissions to limit the impact of future warming.

Spatial and Seasonal Variations of Water and Salt Movement in the Vadose Zone at Salt-Impacted Sites

Oilfield-produced brine is a major source of salt contamination in soil and groundwater. Salt transport in the upper soil layers is controlled by the atmospheric interactions via infiltration of meteoritic water. In lower layers, it is controlled by fluctuations in the groundwater table, which are also linked to atmospheric interactions via groundwater recharge. Therefore, climate is an important factor in the movement of contaminants in the unsaturated zone. A one-dimensional variably saturated flow and transport model with soil atmospheric boundary conditions was used to estimate the effect of climate type and soil texture on soil water and salt dynamics in variably saturated soils. Numerical simulations were run with Hydrus-1D, using daily climate data. Simulations were run for nine-year climate datasets for different ecoclimatic locations in Alberta, Canada. Results indicated that coarse-grained materials are good evaporation barriers, resulting in water gain conditions at the ground surface, irrespective of the climate type. However, the quantity of water gain and associated advective fluxes are a function of climate. Results also indicated that flow and transport in fine-textured soils is more dependent on the climate type. For fine-grained soils in arid climatic conditions, net water loss at the ground surface and upward migration of salt can be expected. For wetter climates, the upward migration of salt is less probable.

Observed Key Surface Parameters for Characterizing Land–Atmospheric Interactions in the Northern Marginal Zone of the Taklimakan Desert, China

An observational data set of the year 2010 at a site in the northern marginal zone of the Taklimakan Desert (TD) was used to analyse the key surface parameters in land–atmospheric interactions in the desert climate of northwest China. We found that the surface albedo (α) and emissivity (ε) were 0.27 and 0.91, respectively, which were consistent with the values obtained based on observations in the hinterland of the TD as well as being similar to the dry parts of the Great Basin desert in North America, where they were comparable to the α and ε values retrieved from remote sensing products. Peak frequency value of z0m was 5.858 × 10−3 m, which was similar to the Mojave Desert, Peruvian desert, Sonoran Desert, HEIFE (Heihe region) Desert, and Badain Jaran Desert. The peak frequency value of z0h was 1.965 × 10−4 m, which was different from those obtained in the hinterland of the TD. The average annual value of excess resistance to heat transfer (kB−1) was 2.5, which was different from those obtained in the HEIFE Gobi and desert, but they were similar to those determined for the Qinghai–Tibetan Plateau and HAPEX-Sahel. Both z0m and z0h varied less diurnally but notably seasonally, and kB−1 exhibited weak diurnal and seasonal variations. We also found that z0m was strongly influenced by the local wind direction. There were many undulating sand dunes in the prevailing wind and opposite to the prevailing wind, which were consistent with the directions of the peak z0m value. The mean values calculated over 24 h for Cd and Ch were 6.34 × 10−3 and 5.96 × 10−3, respectively, which were larger than in the Gobi area, hinterland of the TD and semiarid areas, but similar to HEIFE desert. Under the normal prevailing (NNE–ESE) wind, the mean bulk transfer coefficient Cd and Ch were of the same order of magnitude as expected based on similarity theory. Using the data obtained under different wind directions, we determined the relationships between Cd, Ch, the wind speed U, and stability parameter z/L, and the results were different. Cd and Ch decreased rapidly as the wind speed dropped below 3.0 m s−1 and their minimum values reached around 1–2 m s−1. It should also be noted that the ε values estimated using the sensible heat flux (H) were better compared with those produced using other estimation methods.