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approaches, ranging from properties of the African easterly jet (AEJ) affecting wave development, intrinsic properties of the waves, mechanisms affecting the intensification of waves, to the actual occurrence of tropical cyclones (TCs). Notwithstanding the complexity of the tropical genesis and development problem and the prominent roles of vertical stability and precursor disturbances, it is widely accepted that sea surface temperatures and vertical shear (e.g., Shapiro and Goldenberg 1998 ; Aiyyer
approaches, ranging from properties of the African easterly jet (AEJ) affecting wave development, intrinsic properties of the waves, mechanisms affecting the intensification of waves, to the actual occurrence of tropical cyclones (TCs). Notwithstanding the complexity of the tropical genesis and development problem and the prominent roles of vertical stability and precursor disturbances, it is widely accepted that sea surface temperatures and vertical shear (e.g., Shapiro and Goldenberg 1998 ; Aiyyer
1. Introduction This article investigates African easterly waves (AEWs) with the goals of understanding different regimes and unveiling teleconnections with the extratropics. Disturbances with time scales of about 2–5 days developing over Africa and the tropical Atlantic at latitudes between the African easterly jet (AEJ) and the intertropical convergence zone (ITCZ), with wavelengths ranging from 2000 to 4000 km and propagation speeds of about 15 m s −1 , have been known for a long time (e
1. Introduction This article investigates African easterly waves (AEWs) with the goals of understanding different regimes and unveiling teleconnections with the extratropics. Disturbances with time scales of about 2–5 days developing over Africa and the tropical Atlantic at latitudes between the African easterly jet (AEJ) and the intertropical convergence zone (ITCZ), with wavelengths ranging from 2000 to 4000 km and propagation speeds of about 15 m s −1 , have been known for a long time (e
1. Introduction The boreal summer extratropical circulation lacks the strong jets and large-amplitude stationary waves that typify the boreal winter climate. This, together with the presence of pervasive tropical easterlies that inhibit remote forcing from the tropics, tends to limit boreal summer middle-latitude variability to more local/regional processes, with mesoscale convective weather systems and land–atmosphere coupling playing important roles (e.g., Parker and Johnson 2000 ; Koster
1. Introduction The boreal summer extratropical circulation lacks the strong jets and large-amplitude stationary waves that typify the boreal winter climate. This, together with the presence of pervasive tropical easterlies that inhibit remote forcing from the tropics, tends to limit boreal summer middle-latitude variability to more local/regional processes, with mesoscale convective weather systems and land–atmosphere coupling playing important roles (e.g., Parker and Johnson 2000 ; Koster
, the contour interval is 1 rad −1 , the thick line represents the 0.01 contour and the dashed line indicates the position of the vertical reflecting surface. Finally, the shading indicates regions of wave evanescence in the meridional ( l 2 < 0 bounded by solid line) and vertical ( m 2 < 0 bounded by dashed line) directions. The October–November bounded wave geometry coincides with a particular configuration of the stratospheric eastward jet. Figure 3 shows the zonal-mean zonal wind during
, the contour interval is 1 rad −1 , the thick line represents the 0.01 contour and the dashed line indicates the position of the vertical reflecting surface. Finally, the shading indicates regions of wave evanescence in the meridional ( l 2 < 0 bounded by solid line) and vertical ( m 2 < 0 bounded by dashed line) directions. The October–November bounded wave geometry coincides with a particular configuration of the stratospheric eastward jet. Figure 3 shows the zonal-mean zonal wind during
from GES DISC. (The GPCP data can be downloaded from the Web site http://precip.gsfc.nasa.gov. ) We also thank three anonymous reviewers for comments that improved the manuscript. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This work is supported by the JPL AIRS project, NASA Energy and Water Cycle Study (NEWS), and NASA MEaSUREs. REFERENCES Allen
from GES DISC. (The GPCP data can be downloaded from the Web site http://precip.gsfc.nasa.gov. ) We also thank three anonymous reviewers for comments that improved the manuscript. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This work is supported by the JPL AIRS project, NASA Energy and Water Cycle Study (NEWS), and NASA MEaSUREs. REFERENCES Allen
, 16 , 571 – 591 . Grachev , A. A. , C. W. Fairall , and E. F. Bradley , 2000 : Convective profile constants revisited . Bound.-Layer Meteor. , 94 , 495 – 515 . Helfand , H. M. , and S. D. Schubert , 1995 : Climatology of the simulated Great Plains low-level jets and its contribution to the continental moisture budget of the United States . J. Climate , 8 , 784 – 806 . Holtslag , A. A. M. , and H. A. R. de Bruin , 1988 : Applied modeling of the nighttime surface energy
, 16 , 571 – 591 . Grachev , A. A. , C. W. Fairall , and E. F. Bradley , 2000 : Convective profile constants revisited . Bound.-Layer Meteor. , 94 , 495 – 515 . Helfand , H. M. , and S. D. Schubert , 1995 : Climatology of the simulated Great Plains low-level jets and its contribution to the continental moisture budget of the United States . J. Climate , 8 , 784 – 806 . Holtslag , A. A. M. , and H. A. R. de Bruin , 1988 : Applied modeling of the nighttime surface energy
on the downstream flow: An idealized modelling study with a straight jet . Quart. J. Roy. Meteor. Soc. , 134 , 69 – 91 . Rienecker , M. , and Coauthors , 2011 : MERRA: NASA's Modern-Era Retrospective Analysis for Research and Applications . J. Climate , 24 , 3624 – 3648 . Saha , S. , and Coauthors , 2010 : The NCEP climate forecast system reanalysis . Bull. Amer. Meteor. Soc. , 91 , 1015 – 1057 . Schenkel , B. , and R. Hart , 2010 : An examination of the spatial and
on the downstream flow: An idealized modelling study with a straight jet . Quart. J. Roy. Meteor. Soc. , 134 , 69 – 91 . Rienecker , M. , and Coauthors , 2011 : MERRA: NASA's Modern-Era Retrospective Analysis for Research and Applications . J. Climate , 24 , 3624 – 3648 . Saha , S. , and Coauthors , 2010 : The NCEP climate forecast system reanalysis . Bull. Amer. Meteor. Soc. , 91 , 1015 – 1057 . Schenkel , B. , and R. Hart , 2010 : An examination of the spatial and
observations should enable improved spatial resolution and soil moisture retrieval accuracy under higher biomass levels, with potentially improved assimilation value and reanalysis accuracy. Meanwhile, the GEOS assimilation system will be continually updated and advances in climate modeling and data assimilation will all contribute to better representation of land surface processes in the future analysis products. Acknowledgments Portions of this work were conducted at the Jet Propulsion Laboratory
observations should enable improved spatial resolution and soil moisture retrieval accuracy under higher biomass levels, with potentially improved assimilation value and reanalysis accuracy. Meanwhile, the GEOS assimilation system will be continually updated and advances in climate modeling and data assimilation will all contribute to better representation of land surface processes in the future analysis products. Acknowledgments Portions of this work were conducted at the Jet Propulsion Laboratory
