ALBERT

Description: [1]  The Weather Research and Forecasting (WRF) model was applied to analyze variations in the planetary boundary layer (PBL) structure over southeast (SE) England including central and suburban London. The parameterizations and predictive skills of two nonlocal mixing PBL schemes, YSU and ACM2, and two local mixing PBL schemes, MYJ and MYNN2 were evaluated over a variety of stability conditions, with model predictions at a 3 km grid spacing. The PBL height predictions, which are critical for scaling turbulence and diffusion in meteorological and air quality models, show significant intra-scheme variance (〉 20%) and the reasons are presented. ACM2 diagnoses the PBL height thermodynamically using the bulk Richardson number method, which leads to a good agreement with the lidar data for both unstable and stable conditions. The modeled vertical profiles in the PBL, such as wind speed, turbulent kinetic energy (TKE) and heat flux, exhibit large spreads across the PBL schemes. The TKE predicted by MYJ were found to be too small and show much less diurnal variation as compared with observations over London. MYNN2 produces better TKE predictions at low levels than MYJ, but its turbulent length scale increases with height in the upper part of the strongly convective PBL, where it should decrease. The local PBL schemes considerably underestimate the entrainment heat fluxes for convective cases. The nonlocal PBL schemes exhibit stronger mixing in the mean wind fields under convective conditions than the local PBL schemes and agree better with large-eddy simulation (LES) studies.

Description: The intellectual and cultural dimensions of the science of meteorology and its applications are now widely appreciated. The revolutions in worldwide media and communication technology enable the public and decision-makers to be much better informed about the present and future state of weather, environment and climate, and their practical implications. Non-specialists can now understand and engage in debating some of the main scientific questions facing meteorologists. The institutional and political issues associated with these developments are discussed, particularly the organizational arrangements for the measurement, forecasting, exchange of data and public communication. The effectiveness and functioning of national meteorological services (NMS) and international organizations involved in meteorology depend on their financing and governance, and also their policies for the exchange of data. These factors also affect how they collaborate with other public and private organizations, especially those in related sciences and technologies. Advances in science and computing are progressively improving the accuracy and reliability of weather forecasting and climate predictions, including estimates of their intrinsic limitations. The Internet, which is providing a greater variety of meteorological data to members of the public, also enables them to contribute, not only as voluntary observers and in assisting with warnings of extreme events, but even in participating in computer experiments about climate predictions. The public as well as weather professionals now also provide valuable feedback to forecasting organizations. The role of meteorology becomes even more central to societies as they prepare for the dangers associated with significant changes in climate and environment caused by human activities. Policies to reduce these dangers have to be based on predicting future climate trends, taking into account how societies will respond to these dangers over periods of decades and centuries. There are doubts as to whether emissions of greenhouse gases will be reduced soon enough to avoid critical changes to the environment; failing that, what local and/or global measures might be taken to moderate climate change artificially? Suggestions are made about a better understanding between meteorology, government and society to deal with such issues. Copyright © 2012 Royal Meteorological Society

Description: Some of the highest summer monsoon rainfall in South Asia falls on the windward slopes of the Western Ghats mountains on India's west coast and offshore over the eastern Arabian Sea. Understanding of the processes determining the spatial distribution and temporal variability of this region remains incomplete. In this paper, new Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) aircraft and ground‐based measurements of the summer monsoon over the Western Ghats and upstream of them are presented and placed within the context of remote sensing observations and reanalysis. The transition from widespread rainfall over the eastern Arabian Sea to rainfall over the Western Ghats is documented in high spatial and temporal resolution. Heavy rainfall offshore during the campaign was associated primarily with mid‐tropospheric humidity, secondarily with sea surface temperature, and only weakly with orographic blocking. A mid‐tropospheric dry intrusion suppressed deep convection offshore in the latter half of the campaign, allowing the build‐up of low‐level humidity in the onshore flow and enhancing rainfall over the mountains. Rainfall on the lee side of the Western Ghats occurred during the latter half of the campaign in association with enhanced mesoscale easterly upslope flow. Diurnal cycles in rainfall offshore (maximum in the morning) and on the mountains (maximum in the afternoon) were observed. Considerable zonal and temporal variability was seen in the offshore boundary layer, suggesting the presence of convective downdrafts and cold pools. Persistent drying of the subcloud mixed layer several hundred kilometres off the coast was observed, suggesting strong mixing between the boundary layer and the free troposphere. These observations provide quantitative targets to test models and suggest hypotheses on the physical mechanisms determining the distribution and variability in rainfall in the Western Ghats region. This article is protected by copyright. All rights reserved.