An analytical study of easterly waves over southern peninsular India during the northeast monsoon 2010

Easterly wave characteristics over southern peninsular India during the northeast monsoon season of 2010 are examined by means of synergetic analysis involving synoptic, statistical and numerical methods. NCEP 6-hourly reanalysis datasets of zonal and meridional winds, vertical velocity, temperature and net long wave radiation at 2.5° × 2.5° grid resolution for the period 20th October to 31st December, 2010 form the main database for the analysis. During this period, 3 easterly waves could be identified to have passed over this region and the time period of these waves are determined to be 4.2 days (4.5 days) by statistical methods (synoptic methods). The speed of movement, wavelength and amplitude of the waves are determined to be 7.28 ms-1, 2800 km and 6.7 ms-1 respectively. While rising motion is observed at most of the tropospheric levels over and behind the trough, subsidence occurs ahead of the trough. Divergence is noted over and behind the trough at upper troposphere while convergence occurs in the lower to mid-troposphere. Concomitantly warming is noted ahead of the trough while colder anomalies are noted in the lower levels over and behind the trough.

Effect of monsoon depression of east coast at some distant region in west

Whenever a vortex or system of low or depression forms over head bay during Monsoon months, the west coast experiences heavy rainfall. These heavy rainfall occurrences are usually higher than the normal rainfall. An attempt has been made in this study to visualise the easterly wave model during monsoon months with the help of satellite imageries. The rain is expected heavy and wide spread over Madhya Maharashtra and South Gujarat when third sector of the wave covers these areas, as visualised in satellite wave and depression or vortex lies in the 5th or 6th sector of the wave.

Smoke in the river: an AEROCLO-sA case study

The formation of a river of smoke crossing southern Africa is investigated during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign in September 2017. A complementary set of global and mesoscale numerical simulations as well as ground-based, airborne and space-borne observations of the dynamics, thermodynamics and composition of the atmosphere are used to characterize the river of smoke in terms of timing and vertical extent of the biomass burning aerosol (BBA) layer. The study area was under the synoptic influence of a coastal low rooted in a tropical easterly wave, a high-pressure system over the continent and westerly waves in mid-latitudes, one of which had an embedded cut-off low (CoL). The coastal low interacted with the second of two approaching westerly waves and ultimately formed a mid-level temperate tropical trough (TTT). The TTT created the fast moving air mass transported to the southwestern Indian Ocean as a river of smoke. The CoL, which developed and intensified in the upper levels associated with the first (easternmost) westerly wave, remained stationary above northern Namibia prior to the formation of the TTT and was responsible for the thickening of the BBA layer. This shows that the evolution of the river of smoke is very much tied to the evolution of the TTT while its vertical extent is related to the presence of the CoL. The mechanisms by which the CoL, observed over Namibia in the entrance region of the river of smoke, influences the vertical structure of the BBA layer is mainly associated with the ascending motion above the BBA layer. In the presence of the CoL, the top of the BBA layer over northern Namibia reaches altitudes above 8 km. This is much higher than the average height of the top of the BBA layer over the regions where the smoke comes from (Angola, Zambia, Zimbabwe, Mozambique) which is 5 to 6 km. The results suggest that the interaction between the TTTs and the CoLs which form during the winter may have a role in promoting the transport of BBA from fire-prone regions in the tropical band to the temperate mid-latitudes and southwestern Indian Ocean.

Intense Precipitation and Area of Risk: A Case Study of Mass Movement in the City of Natal, Brazil

This study aims to analyze the atmospheric conditions associated with an event of intense precipitation caused by Easterly Wave Disturbances (EWDs), as well as the environmental conditions related to the mass gravitational movement that occurred between 14th June and 15th June of 2014, in the district of Mãe Luiza, Natal/RN/Brazil. The synoptic conditions, the vertical integrated moisture flux and the energetic behavior in the EWD’s performance phases were analyzed. In addition to these factors, local environmental aspects were assessed, classifying the vulnerability to disaster events in the affected area. Over the days of the operation of the atmospheric system, the daily accumulation of precipitation was greater than 100 mm, with precipitation accumulated in 3 h in the order of 60 mm for the stages of maturation of the disturbance. The main synoptic conditions associated with EWDs were exhibited by the intense anomalies of wind speed and high humidity flux on the east coast of the Northeast, which intensified the influx of moisture into the continent over the period of the operation of the system. Conditions of high to very high vulnerability were identified in the area where the event took place and also in other expressive parts of the district.

Transitional Wave Climate Regions on Continental and Polar Coasts in a Warming World

We provide a comprehensive analysis of the spatial-temporal changes in the atmospheric-driven major wave climates (easterlies, southerlies, and westerlies) under two different Representative Concentration Pathways, the RCP2.6 and RCP8.5 scenarios for the end-of-the-century (2075–2099). By comparing the projected scenarios with historical conditions, we found that the easterly wave climates will be more frequents in the southwest basins (up to 15%) and the southerlies in the eastern basins (up to 20%). While the westerlies are projected to reduce their presence in the mid-latitudes and intensify for the high latitudes associated with the poleward extratropical circulation. As a result, coastal risk will be triggered in transitional wave climate regions, in addition to the risk induced by sea-level rise and storm wave generated, by spatial and frequency changes in the prevailing wave climates that will reach regions where up to now they have not, impacting future coastal environments.

Genesis of an East Pacific Easterly Wave from a Panama Bight MCS: A Case Study Analysis from June 2012

This study investigates the transition of a Panama Bight mesoscale convective system (MCS) into the easterly wave (EW) that became Hurricane Carlotta (2012). Reanalysis, observations, and a convective-permitting Weather Research and Forecasting (WRF) Model simulation are used to analyze the processes contributing to EW genesis. A vorticity budget analysis shows that convective coupling and vortex stretching are very important to the transition in this case, while horizontal advection is mostly responsible for the propagation of the system. In the model, the disturbance is dominated by stratiform vertical motion profiles and a midlevel vortex, while the system is less top-heavy and is characterized by more prominent low-level vorticity later in the transition in reanalysis. The developing disturbance starts its evolution as a mesoscale convective system in the Bight of Panama. Leading up to MCS formation the Chocó jet intensifies, and during the MCS-to-EW transition the Papagayo jet strengthens. Differences in the vertical structure of the system between reanalysis and the model suggest that the relatively more bottom-heavy disturbance in reanalysis may have stronger interactions with the Papagayo jet. Field observations like those collected during the Organization of Tropical East Pacific Convection (OTREC) campaign are needed to further our understanding of this east Pacific EW genesis pathway and the factors that influence it, including the important role for the vertical structure of the developing disturbances in the context of the vorticity budget.