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Author: Tao Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Two mechanisms appear to be primarily responsible for the formation of cirrus clouds in Tropical Tropopause Layer (TTL): detrainment from deep convective anvils and in situ initiation. Here we propose to identify TTL cirrus clouds by analyzing water content measurements from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aura Microwave Limb Sounder (MLS). Using ice water content (IWC) and water vapor (H2O) abundances we identify TTL cirrus clouds that contain too much ice to have been formed in situ -- and therefore must be of convective origin. We use two methods to infer amounts of water vapor available for in situ formation. Clouds with IWC greater than this threshold are categorized as being of convective origin; clouds with IWC below the threshold are ambiguous -- they could either form from in situ or still be of convective origin. Applying the thresholds from December 2008 to November 2009, we found that at least 19.2% of tropical cirrus were definitively of convective origin at the tropopause (375 K) during boreal winter. At each level, we found three maxima in the occurrence of convective cirrus: western Pacific, equatorial Africa, and South America. Averaged over the entire tropics (30oS to 30oN), we found convective cirrus occurs more frequently in boreal winter and less frequently in boreal summer, basically following the a decreasing trend from DJF, MAM, SON, to JJA. During boreal summer, we found that only 4.6% of tropical cirrus come from convection. Sensitivity tests show that the thresholds derived at 390 K have the largest uncertainty. At lower levels, especially 375 K, our thresholds are robust.
Author: Tao Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Two mechanisms appear to be primarily responsible for the formation of cirrus clouds in Tropical Tropopause Layer (TTL): detrainment from deep convective anvils and in situ initiation. Here we propose to identify TTL cirrus clouds by analyzing water content measurements from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aura Microwave Limb Sounder (MLS). Using ice water content (IWC) and water vapor (H2O) abundances we identify TTL cirrus clouds that contain too much ice to have been formed in situ -- and therefore must be of convective origin. We use two methods to infer amounts of water vapor available for in situ formation. Clouds with IWC greater than this threshold are categorized as being of convective origin; clouds with IWC below the threshold are ambiguous -- they could either form from in situ or still be of convective origin. Applying the thresholds from December 2008 to November 2009, we found that at least 19.2% of tropical cirrus were definitively of convective origin at the tropopause (375 K) during boreal winter. At each level, we found three maxima in the occurrence of convective cirrus: western Pacific, equatorial Africa, and South America. Averaged over the entire tropics (30oS to 30oN), we found convective cirrus occurs more frequently in boreal winter and less frequently in boreal summer, basically following the a decreasing trend from DJF, MAM, SON, to JJA. During boreal summer, we found that only 4.6% of tropical cirrus come from convection. Sensitivity tests show that the thresholds derived at 390 K have the largest uncertainty. At lower levels, especially 375 K, our thresholds are robust.
Author: Hsiu-Hui Tseng
Publisher:
ISBN:
Category :
Languages : en
Pages : 46
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This study examines the spatial and temporal patterns of tropical tropopause layer (TTL) cirrus clouds (i.e., clouds with bases higher than 14.5 km) and their relationship to tropical tropopause including both cold point tropopause (CPT) and lapse rate tropopause (LRT). We use eight years (2006–2014) data from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements. In addition to the CALIPSO cloud layer product, the clouds included in the current CALIPSO dataset as stratospheric features have been considered by separating clouds from aerosols, which are important in the TTL cloud analysis. It is also shown that the temporal variation of the stratospheric aerosols matches well with the volcanic eruption events.The TTL cloud fraction and the tropical tropopause temperature both have pronounced annual cycles and are strongly negatively correlated both temporally and spatially. The examination of the TTL cloud height relative to tropopause from collocated CALIPSO and COSMIC observations indicates that the tropopause plays a critical role in constraining the TTL cloud top height. We show that the probability density function of TTL cloud top height peaks just below the CPT while the occurrence of TTL clouds with cloud tops above the CPT could be largely explained by observed tropopause height uncertainty associated with the COSMIC vertical resolution.
Author: Kai-Wei Chang
Publisher:
ISBN:
Category : Stratospheric circulation
Languages : en
Pages : 0
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As a gateway of troposphere-to-stratosphere transport, the tropical tropopause layer (TTL) plays a key role in determining the concentration and distribution of water vapor in the upper troposphere and lower stratosphere (UTLS). This dissertation presents three studies on the dynamical and radiative processes that influence the TTL and also the Brewer-Dobson circulation (BDC) in the global UTLS. Water vapor in the tropical lower stratosphere is strongly correlated with TTL temperatures, which are closely associated with latent heating (LH) in tropical convection. The first study examines the role of latent heating (LH) vertical distribution in TTL cooling and upper-tropospheric warming associated with equatorial wave responses. Using cross-spectral analysis on time series of LH and UTLS temperature, we show that heating above 6 km was found to have the highest coherence with the equatorial wave cooling and warming pattern in the mean temperature profile. We distinguish the effects of convective and stratiform LH, whose heating altitudes differ. Stratiform LH exhibits higher coherence with temperature throughout the UTLS, especially in the equatorial Rossby wave response as seen in the cross-spectral analysis. Highest coherences occur mostly at time scales of the Madden-Julian Oscillation (MJO), suggesting the importance of MJO convection in TTL cooling and subsequent dehydration processes. The second study explores the relationship of TTL cirrus clouds to gravity and Kelvin waves. Motivated by the recent interest in understanding how the vertical gradient of temperature anomalies (dT'/dz) from waves influence clouds, we collocate lidar observations of TTL clouds and wave temperature anomalies from radio occultation to understand how cloud occurrence relates to wave anomalies. Throughout the TTL, 57% of clouds were found in the wave phases where both the temperature anomaly (T') and dT'/dz were negative. In contrast, 24% of clouds were in the phase of negative T' but positive dT'/dz, suggesting that regions of negative dT'/dz significantly promote the formation and/or maintenance of clouds. We show that larger (smaller) values T' are associated with a lower (higher) probability of cloud occurrence, demonstrating connection of wave amplitude to TTL cloud formation. The BDC is a balance between wave-mean-flow interaction and radiative heating rates in the middle atmosphere. Since clouds modulate the amount of upwelling radiation, they can also influence the radiative heating in the UTLS. Using the CloudSat/CALIPSO 2B-FLXHR-LIDAR data set and the MERRA-2 reanalysis, the final study evaluates cloud effects on the BDC by comparing the mass circulation diagnosed from clear-sky and all-sky radiative heating rates. Cloud effects are strongest during boreal winter when the vertical and meridional components of the BDC below 80 hPa exhibit differences on the order of 0.1 mm/s and 10 cm/s, respectively. These magnitudes are comparable to the BDC itself, illustrating that cloud effects on radiative heating rates can have a significant influence on the strength of tropical upwelling and meridional mixing. TTL cirrus, which tends to impose weak heating in the TTL, were found to enhance the tropical upwelling and also the poleward transport, while the aggregate effect of all other cloud types was to weaken them instead.
Author:
Publisher:
ISBN:
Category : Geophysics
Languages : en
Pages : 444
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Book Description
Author: Kuo-Nan Liou
Publisher: Cambridge University Press
ISBN: 0521889162
Category : Science
Languages : en
Pages : 461
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Book Description
This volume outlines the fundamentals and applications of light scattering, absorption and polarization processes involving ice crystals.
Author: Mekonnen Gebremichael
Publisher: Springer Science & Business Media
ISBN: 904812915X
Category : Science
Languages : en
Pages : 327
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Book Description
With contributions from a panel of researchers from a wide range of fields, the chapters of this book focus on evaluating the potential, utility and application of high resolution satellite precipitation products in relation to surface hydrology.
Author: John P. Burrows
Publisher: Springer Science & Business Media
ISBN: 3642147917
Category : Technology & Engineering
Languages : en
Pages : 576
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Book Description
The impact of anthropogenic activities on our atmospheric environment is of growing public concern and satellite-based techniques now provide an essential component of observational strategies on regional and global scales. The purpose of this book is to summarise the state of the art in the field in general, while describing both key techniques and findings in particular. It opens with an historical perspective of the field together with the basic principles of remote sensing from space. Three chapters follow on the techniques and on the solutions to the problems associated with the various spectral regions in which observations are made. The particular challenges posed by aerosols and clouds are covered in the next two chapters. Of special importance is the accuracy and reliability of remote sensing data and these issues are covered in a chapter on validation. The final section of the book is concerned with the exploitation of data, with chapters on observational aspects, which includes both individual and synergistic studies, and on the comparison of global and regional observations with chemical transport and climate models and the added value that the interaction brings to both. The book concludes with scientific needs and likely future developments in the field, and the necessary actions to be taken if we are to have the global observation system that the Earth needs in its present, deteriorating state. The appendices provide a comprehensive list of satellite instruments, global representations of some ancillary data such as fire counts and light pollution, a list of abbreviations and acronyms, and a set of colourful timelines indicating the satellite coverage of tropospheric composition in the foreseeable future. Altogether, this book will be a timely reference and overview for anyone working at the interface of environmental, atmospheric and space sciences.
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309467578
Category : Science
Languages : en
Pages : 717
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Book Description
We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet presents prioritized science, applications, and observations, along with related strategic and programmatic guidance, to support the U.S. civil space Earth observation program over the coming decade.
Author: K. N. Liou
Publisher: Academic Press
ISBN: 0124514510
Category : Nature
Languages : en
Pages : 599
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Book Description
Fundamentals of radiation for atmospheric applications -- Solar radiation at the top of the atmosphere -- Absorption and scattering of solar radiation in the atmosphere -- Thermal infrared radiation transfer in the atmosphere -- Light scattering by atmospheric particulates -- Principles of radiative transfer in planetary atmospheres -- Application of radiative transfer principles to remote sensing -- Radiation and climate.
Author: David G. Andrews
Publisher: Academic Press
ISBN: 0080954677
Category : Science
Languages : en
Pages : 502
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Book Description
For advanced undergraduate and beginning graduate students in atmospheric, oceanic, and climate science, Atmosphere, Ocean and Climate Dynamics is an introductory textbook on the circulations of the atmosphere and ocean and their interaction, with an emphasis on global scales. It will give students a good grasp of what the atmosphere and oceans look like on the large-scale and why they look that way. The role of the oceans in climate and paleoclimate is also discussed. The combination of observations, theory and accompanying illustrative laboratory experiments sets this text apart by making it accessible to students with no prior training in meteorology or oceanography. * Written at a mathematical level that is appealing for undergraduates and beginning graduate students * Provides a useful educational tool through a combination of observations and laboratory demonstrations which can be viewed over the web * Contains instructions on how to reproduce the simple but informative laboratory experiments * Includes copious problems (with sample answers) to help students learn the material.
