Distinguishing High Cloud and Atmospheric Composition Features from East and West Tropical Pacific Observations …
Figure 1 (below) shows a summary of the main structure and features of an overshooting convective plume that frequently form at the tropics, as identified in Section 5.3*.
The analysis uses data from ice water content, water vapour, ozone (version 2 MLS products); liquid water content, vertical wind tendencies (European Center for Medium-range Weather Forecasts Re-Analysis Interim data); outgoing longwave radiation (Clouds and the Earth’s Radiant Energy System Single Scanner Footprint data product in Flight Mode 3); and simulated Outgoing Longwave Radiation (OLR) and longwave radiative heating rates (Atmospheric and Environmental Research Rapid Radiative Transfer Model – Longwave component).
Using a combination of NASA (Aura) Microwave Limb Sounder (MLS) measurements and radiative transfer outputs a deep convective plume is defined by cloud ice water content measurements above 4 mg per cubic metre that extend from 261 hPa (the mid-troposphere) to pressures below 150 hPa, which represents a continuous deep region of moist convection in the sub-zero troposphere.
Near neutral longwave radiative heating rates (LW HRs) are used to identify the tropopause e.g. Andrews (2000), associated with the cold-dry signal of the tropopause at ~20km (100 hPa). The field of view of the MLS instrument at 240 GHz indicates an uncertainty of ~50 hPa in the vertical MLS position, as estimated in Chapter 4, which is considered in our identification of tropical clouds with anvils. As deep convection extend the low to mid-troposphere, further confidence of their detection can be provided by identifying those regions where higher MLS water vapour mixing ratios are present from the surface to 400 hPa. This cannot include the mixed-phase region of atmosphere, since this part of the troposphere is not well specified by measurement data.
Figure 1. Schematic showing the main features of high cloud features from tropical case study analysis: Key features of tropical troposphere scenes (clouds in white) identified from co-located measurement data from MLS (Aura), ECMWF ERA-Interim and the AER RRTM LW. The analysis summarises findings from case study data from 19th September, 2004 (two case studies). Tile 1 shows a cross-equatorial transect of high clouds with altitude and latitude indicated by the vertical and horizontal plane of the schematic and latitudes relative to the Inter-Tropical Convergence Zone (ITCZ). A red circle indicates the position of the subtropical jet-stream, whilst the red arrows indicate the relative amounts of Outgoing Longwave Radiation (OLR). Tiles 2 and 3 show the sub-structure of the high clouds of the ITCZ (centre of Tile 1), indicating the mesoscale convective clouds with an anvil and the location of maximum longwave radiative heating (HRLW). Tile 3 shows the finer structure of the same cumulonimbus clouds and relative vertical motions (thick black arrows). Tile 4 (top) shows the anvil cloud within the Tropical Tropopause Layer (TTL), with stratospheric exchange of ozone (O3) and water vapour (WV) and outflow of ice particles indicated by black arrows. This figure is not to scale. *Copyright Dr CJ Nankervis, 2013.
*Nankervis, C.J. (2013) “Co-located Analysis of Ice Clouds Detected from Space and their Impact on the Longwave Radiation Budget“. Published PhD thesis. University of Edinburgh – See more at: http://www.era.lib.ed.ac.uk/handle/1842/7755
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 Copyright © 2002-2010, Atmospheric and Environmental Research, Inc. (AER, Inc.)
All work undertaken at the University of Edinburgh in the School of GeoSciences. Rights remain with author; Dr Christopher J Nankervis, 2013. Findings summarised and extracted from Chapter 5 of PhD thesis.