El Niño Modoki connection to extremely-low streamflow of the Paranaíba River in Brazil

Extremely-low discharge events of the Paranaíba River basin during the austral summer season (December–February, DJF), are found to be associated with the Pacific sea surface temperature anomalies resembling the recently identified El Niño Modoki phenomenon. Extreme discharge events are identified based on their persistent flow for 7 days and more after taking retention time into consideration. Ninety percent of the extremely low discharge events during peak streamflow seasons of DJF, are found to occur during the El Niño Modoki years. A diagnostics study of atmospheric anomalies has shown a clear connection between the modified Walker circulation, associated with the El Niño Modoki, and the precipitation anomalies over the Paranaíba River basin. The climate variations have direct relationship with the rainfall. Streamflow variations are considered as the surrogates to rainfalls. Thus, El Niño Modoki phase is important component to understand and predict the streamflow variations in the Paranaíba River basin.     

Impact of cyclone Nilam on tropical lower atmospheric dynamics

A deep depression formed over the Bay of Bengal on 28 October 2012, and developed into a cyclonic storm. After landfall near the south coast of Chennai, cyclone Nilam moved north-northwestwards. Coordinated experiments were conducted from the Indian stations of Gadanki(13.5?N, 79.2?E) and Hyderabad(17.4?N, 78.5?E) to study the modification of gravity-wave activity and turbulence by cyclone Nilam, using GPS radiosonde and mesosphere–stratosphere–troposphere radar data. The horizontal velocities underwent large changes during the closest approach of the storm to the experimental sites. Hodograph analysis revealed that inertia gravity waves(IGWs) associated with the cyclone changed their directions from northeast(control time) to northwest following the path of the cyclone. The momentum flux of IGWs and short-period gravity waves(1–8 h) enhanced prior to, and during, the passage of the storm(±0.05 m2s-2and ±0.3 m2s-2, respectively), compared to the flux after its passage. The corresponding body forces underwent similar changes, with values ranging between ±2–4m s-1d-1and ±12–15 m s-1d-1. The turbulence refractivity structure constant(C2n) showed large values below 10 km before the passage of the cyclone when humidity in the region was very high. Turbulence and humidity reduced during the passage of the storm when a turbulent layer at ～17 km became more intense. Turbulence in the lower troposphere and near the tropopause became weak after the passage of the cyclone.     

Activity of radon (<Superscript>222</Superscript>Rn) in the lower atmospheric surface layer of a typical rural site in south India

Analysis of one year measurements of in situ radon (²²²Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth’s surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5^°N and 79.2^°E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning hours followed by a remarkable decrease in the afternoon hours. Relatively, a higher concentration of radon was observed at NARL during fair weather days, and this can be attributed to the presence of rocky hills and dense vegetation surrounding the site. The high negative correlation between surface air temperature and activity of radon (R = – 0.70, on an annual scale) suggests that dynamical removal of radon due to increased vertical mixing is one of the most important controlling processes of the radon accumulation in the atmospheric surface layer. The annual averaged activity of radon was found to be 12.01±0.66 Bq m^?3 and 4.25±0.18 Bq m^?3 for its progenies, in the study period.     

Effect of the annular solar eclipse of 15 January 2010 on the lower atmospheric boundary layer over a tropical rural station

This paper documents the effect of the annular solar eclipse of 15 January 2010 on the lower atmospheric boundary layer dynamics over a complex terrain environment at Gadanki (13.5°N, 79.2°E,) using a suite of instruments namely automatic weather station, mini boundary layer mast (15 m), Doppler SODAR, GPS radiosonde and ozonesonde observations. The net heating rates are estimated using radiative transfer algorithm before, during and after the eclipse. Effect on soil temperature is seen clearly up to 20 cm depth and at all the levels up to 15 m. Decrease in the thermal plume level, a dip in the surface layer and a strong vertical downdrafts (subsidence) are noticed during the peak eclipse. Upper layer winds did not show any variation during the eclipse. It is also found to have pronounced effect on all the surface meteorological parameters for a two-day period.     

Consolidation due to shear loads distributed over a rectangular area

The paper presents an analytical study of the consolidation of a semi-infinite clay layer subjected to a shear load distributed over a rectangular area. Biot's theory is made use of, along with the three displacement functions suggested by Verruijt. A complex Fourier and Laplace transformation technique enables the solution to be obtained in terms of non-dimensional parameters. Settlements and pore pressures under the loaded area are evaluated for two types of surface drainage conditions. Extension of the solutions to point loads is also suggested. The Mandel–Cryer effect is seen in the behaviour of the pore pressure.     

Fitting refugees into the normative narrative of Australian multiculturalism

Australia publicly espouses its multiculturalism as a key component of its national identity. In this paper, I argue that despite the importance of multiculturalism to Australia’s identity, political decisions and discourse has muddied its remit with respect to humanitarian migrant intake programs and outcomes. Australia’s history of selective migrant intake and restrictive refugee policy continues the Othering of past policies into contemporary settings. Refugee policy has become a political football. During the most recent national election campaign (May 2019), the plight of sick and ill refugees, currently housed offshore in detention centers, was used as a political pawn. Lost amid this political rhetoric were the traumatic narratives of forced migrants resettling in Australia’s cities. Without possibility for a loud voice in public discourse, there is little opportunity for more Australians to understand how refugees experience detention centers, struggle to attain residency visas, and make “home” in multicultural Australia. I draw on research with Sri Lankan refugees in Sydney to give voice to these micro-level, place-based experiences of vulnerable arrivals. These stories, I think, can (re)shape and enrich Australia’s multicultural identity because they challenge us to not only accept difference but recognize the circumstances through which Australia’s diversity seeds its narrative.     

Sub-daily variations observed in Tropical Easterly Jet (TEJ) streams

To investigate the sub-daily variation in Tropical Easterly Jet (TEJ), a few special experiments have been conducted with mesosphere–stratosphere–troposphere (MST) radar located at Gadanki(13.5°N, 79.2°E) under Study on Atmospheric Forcing and Responses (SAFAR) campaign during 2008–2009. Large sub-daily changes in the TEJ characteristics are observed within a day in addition to day-to-day changes. Based on this observational study, three possible mechanisms for the sub-daily variations are proposed i.e., (1) motion of TEJ core, (2) large updrafts and downdrafts, and (3) strong wave activity. Interestingly, TEJ peak altitude is seen above the Cold Point Tropopause altitude for about 42% of the days.     

Origin of extreme summers in Europe: the Indo-Pacific connection

Extreme summers of Europe are usually affected by blocking highs that shift between Western and Eastern Europe to cause regional variations in the surface temperature anomalies. Generally, the blocking high induces a regional temperature dipole with poles of warm and cold anomalies on two sides of Europe. The extreme summers of Western Europe, when the Eastern Europe is colder than normal, are usually associated with the teleconnections arising from positive Indian Ocean Dipole (IOD) events. In contrast, analogous warm events in Eastern Europe are usually associated with La Niña. The western Pacific conditions that prevail during the turnaround phase of El Niño to La Niña are found to be responsible for developing the extreme Eastern Europe events. The role of North Atlantic Oscillation (NAO) is not blatant for the Eastern Europe summers though it has a weaker influence on Western Europe summers for which IOD plays a dominant role: The seasonal July–August correlation for Western Europe temperature with IOD index is higher than that with the NAO index. The teleconnections for both types of extremes are associated with a Rossby wavetrain that travel around the globe to reach the Europe. This circumglobal teleconnection is largely determined by the location of the tropospheric heat source. For Western Europe warm events, major contributions come from the atmospheric convections/diabatic heating over northwest India and southern Pakistan. For the Eastern Europe events, the convections over northwest Pacific, south of Japan, are found to project the signals on to the mid-latitude wave-guide. These patterns of teleconnection are so robust that those can be seen on daily to seasonal time-scales of atmospheric anomalies. The wavetrains are found to set-in a couple of weeks prior to the development of blocking highs and extreme hot conditions over Europe.     

Simulation of the Indian monsoon using the RegCM3–ROMS regional coupled model

A regional coupled atmosphere–ocean model was developed to study the role of air–sea interactions in the simulation of the Indian summer monsoon. The coupled model includes the regional climate model (RegCM3) as atmospheric component and the regional ocean modeling system (ROMS) as oceanic component. The two-way coupled model system exchanges sea surface temperature (SST) from the ocean to the atmospheric model and surface wind stress and energy fluxes from the atmosphere to the ocean model. The coupled model is run for four years 1997, 1998, 2002 and 2003 and the results are compared with observations and atmosphere-only model runs employing Reynolds SSTs as lower boundary condition. It is found that the coupled model captures the main features of the Indian monsoon and simulates a substantially more realistic spatial and temporal distribution of monsoon rainfall compared to the uncoupled atmosphere-only model. The intraseasonal oscillations are also better simulated in the coupled model compared to the atmosphere-only model. These improvements are due to a better representation of the feedbacks between the SST and convection and highlight the importance of air–sea coupling in the simulation of the Indian monsoon.