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  • 1
    Electronic Resource
    Electronic Resource
    The impact of geophysical parameters on longwave radiation budget at the top and base of the atmosphere (1991)
    Springer
    Meteorology and atmospheric physics 46 (1991), S. 29-40 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The effect of clouds on longwave radiation budget at the top and base of the atmosphere is studied by using the HIRS2/MSU-retrieved temperature and humidity fields, and cloud fields and the International Satellite Cloud Climatology Project-produced fields. Detailed studies are carried out at four selected sites: one at Equatorial Eastern Pacific (ITCZ) area, one at Libyan Desert (Libya), one at Ottawa, Montreal (Ottawa), and one at central Europe (Europe). The monthly mean differences in outgoing longwave radiation (OLR) (the ISCCP-based OLR minus the HIRS2-based OLR), ranging from −2.8 Wm−2 at ITCZ to −15.4 Wm−2 at Ottawa, are less than the monthly mean differences in surface downward flux, ranging from −2.7 Wm−2 at Libya to 40.6 Wm−2 at the ITCZ. The large differences in surface downward flux are mainly due to large differences in cloud amount and moisture in the low levels of the atmosphere. Monthly mean OLR and surface downward flux can be derived either (1) from instantaneous temperature, humidity, and cloud fields over a month period or (2) from monthly mean temperature, humidity, and cloud fields. The monthly mean OLR and surface downward flux derived from the first approach is compared with the second. The differences in OLR are small, ranging from −0.05 Wm−2 to 6.2 Wm−2, and the differences in surface downward flux is also small, ranging from 0.4 Wm−2 to 6.4 Wm−2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026621
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  • 2
    Electronic Resource
    Electronic Resource
    Surface downward flux computed by using geophysical parameters derived from HIRS 2/MSU soundings (1989)
    Springer
    Theoretical and applied climatology 40 (1989), S. 37-51 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Die globalen Felder der emitierten langwelligen Strahlung (OLR) und des nach unten gerichteten Flusses (SDF) werden für Januar und Juli des FGGE-Jahres 1979 berechnet. Die Berechnungen wurden mit Hilfe von geophysikalischen Parametern aus Satellitendaten und einem Strahlungsmodell ausgeführt. Die geophysikalischen Parameter (wie Temperatur-und Feuchtprofile, Oberflächen- bzw. Landtemperatur sowie Bewölkung) werden durch Analysen der HIRS 2/MSU-Daten mit Hilfe des „GLA-Physical Retrieval System“ gewonnen. Das Strahlungsmodell ist ein modifiziertes Modell nach Wu-Kaplan, wie es im Modell der allgemeinen Zirkulation des GLA verwendet wird. Andere Flüsse (wie OLR und SDF bei klarem Himmel, sowie die Emission der Erde), Flußdivergenzen (nach oben gerichtete Fluß- und Nettoflußdivergenz), Flußdifferenzen und langwelliger Strahlungsantrieb (OLR bei klarem und bewölktem Himmel, SDF bei klarem und bewölktem Himmel und der Antrieb durch die Bewölkung), die alle physikalische Bedeutung haben, aber nicht direkt aus dem All gemessen werden können, wurden ebenfalls berechnet und werden hier vorgestellt.
    Notes: Summary The global field of outgoing longwave radiation (OLR) and surface downward flux (SDF) are computed for January and July 1979 (FGGE year). The computation was done by using geophysical parameters retrieved from space in conjunction which a radiation code. The geophysical parameters (such as temperature and humidity profiles, surface/land temperature, and cloud information) are retrieved from analysis of HIRS 2/MSU using the Goddard Laboratory for Atmospheres (GLA) physical retrieval system. The radiation code is a modified version of the Wu-Kaplan radiation code used in the GLA 4th order GCM. Other fluxes (such as clear OLR and clear SDF, and Earth emission) flux divergences (upward flux divergence and net upward flux divergence), flux differences and longwave radiative forcing (clear OLR — cloudy OLR, cloudy SDF — clear SDF, and atmospheric cloud forcing) which have physical meaning but can not be measured directly from space have also been computed and presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867790
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  • 3
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    The impact of geophysical parameters on longwave radiation budget at the top and base of the atmosphere (1991)
    Springer
    Details
    Publication Date: 1991-01-01
    Print ISSN: 0177-7971
    Electronic ISSN: 1436-5065
    Topics: Geography , Physics
    Published by Springer
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  • 4
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    Global precipitation estimates from satellite: Using difference fields of outgoing long‐wave radiation (1991)
    Taylor & Francis
    Details
    Publication Date: 1991-03-01
    Print ISSN: 0705-5900
    Electronic ISSN: 1480-9214
    Topics: Geosciences , Physics
    Published by Taylor & Francis
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  • 5
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    A Characterization of African Easterly Waves on 2.5–6-Day and 6–9-Day Time Scales (2013)
    American Meteorological Society
    Details
    Publication Date: 2013-09-09
    Description: This study shows that the African easterly wave (AEW) activity over the African monsoon region and the northern tropical Atlantic can be divided in two distinct temporal bands with time scales of 2.5–6 and 6–9 days. The results are based on a two-dimensional ensemble empirical mode decomposition (2D-EEMD) of the Modern-Era Retrospective Analysis for Research and Applications (MERRA). The novel result of this investigation is that the 6–9-day waves appear to be located predominantly to the north of the African easterly jet (AEJ), originate at the jet level, and are different in scale and structure from the well-known low-level 2.5–6-day waves that develop baroclinically on the poleward flank of the AEJ. Moreover, they appear to interact with midlatitude eastward-propagating disturbances, with the strongest interaction taking place at the latitudes where the core of the Atlantic high pressure system is located. Composite analyses applied to the mode decomposition indicate that the interaction of the 6–9-day waves with midlatitude systems is characterized by enhanced southerly (northerly) flow from (toward) the tropics. This finding agrees with independent studies focused on European floods, which have noted enhanced moist transport from the ITCZ toward the Mediterranean region on time scales of about a week as important precursors of extreme precipitation.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 6
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    Seasonality and Meridional Propagation of the MJO (2006)
    American Meteorological Society
    Details
    Publication Date: 2006-05-15
    Description: The Madden–Julian oscillation (MJO) is known to have a substantial impact on the variability of the Asian–Australian summer monsoons. An important, but not well understood, aspect of the MJO–monsoon connection is the meridional propagation of bands of enhanced or reduced precipitation that are especially pronounced during the northern summer. In this study, the nature of the seasonality of the MJO is examined, with a focus on the meridional propagation, using both observations and simulations with an atmospheric general circulation model (AGCM). A key result is that the AGCM, when forced with idealized eastward propagating equatorial dipole heating anomalies, reproduces the salient features of the observed seasonality in the precipitation and wind fields associated with the MJO, including meridional propagation into the Indian and Australian summer monsoon regions. An analysis of the simulations and observations shows that the off-equatorial precipitation anomalies are initiated by surface frictional convergence/divergence associated with the Rossby wave response to the leading pole of the equatorial heating dipole. The off-equatorial precipitation anomalies develop further by interacting with the trailing pole of the equatorial dipole heating to produce a northwest–southeast (or southwest–northeast) oriented line of surface convergence/divergence that propagates to the east. Since the prescribed heating does not vary by season, the seasonal asymmetry in the response must be the result of the seasonal changes in the background state. In particular, the results suggest that seasonal changes in both the vertical wind shear and static stability play a role.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 7
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    Forced and Free Intraseasonal Variability over the South Asian Monsoon Region Simulated by 10 AGCMs (2002)
    American Meteorological Society
    Details
    Publication Date: 2002-10-01
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 8
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    African Easterly Jet: Barotropic Instability, Waves, and Cyclogenesis (2012)
    American Meteorological Society
    Details
    Publication Date: 2012-03-01
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 9
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    African Easterly Jet: Structure and Maintenance (2009)
    American Meteorological Society
    Details
    Publication Date: 2009-09-01
    Description: This article investigates the African easterly jet (AEJ), its structure, and the forcings contributing to its maintenance, critically revisiting previous work that attributed the maintenance of the jet to soil moisture gradients over tropical Africa. A state-of-the-art global model in a high-end computer framework is used to produce a three-member 73-yr ensemble run forced by observed SST to represent the control run. The AEJ as produced by the control is compared with the representation of the AEJ in the 40-yr ECMWF Re-Analysis (ERA-40) and other observational datasets and found to be very realistic. Five experiments are then performed, each represented by sets of three-member 22-yr-long (1980–2001) ensemble runs. The goal of the experiments is to investigate the role of meridional soil moisture gradients, different land surface properties, and orography. Unlike previous studies, which have suppressed soil moisture gradients within a highly idealized framework (i.e., the so-called bucket model), terrestrial evaporation control is here achieved with a highly sophisticated land surface treatment and with an extensively tested and complex methodology. The results show that the AEJ is suppressed by a combination of absence of meridional evaporation gradients over Africa and constant vegetation, even if the individual forcings taken separately do not lead to the AEJ disappearance, but only its modification. Moreover, the suppression of orography also leads to a different circulation in which there is no AEJ. This work suggests that it is not just soil moisture gradients but a unique combination of geographical features present only in northern tropical Africa that causes and maintains the jet.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 10
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    An Analysis of Moisture Fluxes into the Gulf of California (2009)
    American Meteorological Society
    Details
    Publication Date: 2009-04-15
    Description: This study examines the nature of episodes of enhanced warm-season moisture flux into the Gulf of California. Both spatial structure and primary time scales of the fluxes are examined using the 40-yr ECMWF Re-Analysis data for the period 1980–2001. The analysis approach consists of a compositing technique that is keyed on the low-level moisture fluxes into the Gulf of California. The results show that the fluxes have a rich spectrum of temporal variability, with periods of enhanced transport over the gulf linked to African easterly waves on subweekly (3–8 day) time scales, the Madden–Julian oscillation (MJO) at intraseasonal time scales (20–90 day), and intermediate (10–15 day) time-scale disturbances that appear to originate primarily in the Caribbean Sea–western Atlantic Ocean. In the case of the MJO, enhanced low-level westerlies and large-scale rising motion provide an environment that favors large-scale cyclonic development near the west coast of Central America that, over the course of about 2 weeks, expands northward along the coast eventually reaching the mouth of the Gulf of California where it acts to enhance the southerly moisture flux in that region. On a larger scale, the development includes a northward shift in the eastern Pacific ITCZ, enhanced precipitation over much of Mexico and the southwestern United States, and enhanced southerly/southeasterly fluxes from the Gulf of Mexico into Mexico and the southwestern and central United States. In the case of the easterly waves, the systems that reach Mexico appear to redevelop/reorganize on the Pacific coast and then move rapidly to the northwest to contribute to the moisture flux into the Gulf of California. The most intense fluxes into the gulf on these time scales appear to be synchronized with a midlatitude short-wave trough over the U.S. West Coast and enhanced low-level southerly fluxes over the U.S. Great Plains. The intermediate (10–15 day) time-scale systems have zonal wavelengths roughly twice that of the easterly waves, and their initiation appears to be linked to an extratropical U.S. East Coast ridge and associated northeasterly winds that extend well into the Caribbean Sea during their development phase. The short (3–8 day) and, to a lesser extent, the intermediate (10–15 day) time-scale fluxes tend to be enhanced when the convectively active phase of the MJO is situated over the Americas.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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