Download or read book Investigating Arctic Cloud and Radiative Properties Associated with the Large scale Climate Variability Through Observations Reanalysis and Mesoscale Modeling written by Neil P. Barton and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation examines two decades of Arctic cloud cover data and the variability in Arctic clouds with relation to changes in sea ice using observational and reanalysis data, as well as a state-of-the-art mesoscale model. Decadal length Arctic cloud cover data are examined because of the inherent differences within these measurements that have not been explored in previous research. Cloud cover data are analyzed from regions poleward of 60°N from several sources of visual surface observations including surface remotely sensed measurements at two locations, two spaced-based passive remotely sensed datasets (Advanced Very High Resolution Radiometer Polar Pathfinder extended (APPx) and Television Infrared Observation Satellite Operational Vertical Sounder (TOVS) Polar Pathfinder (TPP)), and one reanalysis dataset (European Center for Medium-Range Weather Forecasting Reanalysis (ERA-40)) are compared. The passive remotely sensed data are sensitive to surface type. Cloud amounts from the APPx and TPP decrease with increases in sea ice concentrations. In comparison to the surface remotely sensed measurements over sea ice, the APPx and TPP cloud amounts are consistently low. The ERA-40 output cloud cover not contain a sharp decrease from water to ice surfaces, and compares reasonably with the remotely sensed surface measurements over sea ice. During the northern hemisphere winter at land stations, the TPP and ERA-40 cloud amounts are similar. This is most likely a result of the ERA-40 model using TOVS irradiances as input data. The APPx and surface cloud amounts are similar during all seasons, but they are not in precise agreement with the TPP/ERA-40 values. Cloud amounts from the ERA-40 are also most similar to surface measurements in regions where radiosonde data are used as input. Cloud radiative forcing calculated from the ERA-40 output is examined with relation to sea ice concentrations using 20 years of data. The radiative effect of clouds varies linearly with sea ice concentrations during the winter and spring. This relationship is most statistically significant in the North Atlantic region, but statistically significant relationships also occurring the northern Pacific. Statistically significant correlations do not occur during the summer months. By calculating differences in cloud amount during low and high sea ice concentration summers, greater cloud cover amounts occur with decreases in sea ice in the Arctic poleward of the Pacific at the 80 percent statistical significant level. In October, clouds are varying with relation to sea ice near the sea ice edge. One-month lag relationships are calculated to examine if the cloud radiative forcing terms are changing before or after changes in sea ice concentration. Changes in the longwave radiative forcing of clouds occurs before changes in sea ice concentrations and surface temperatures in the North Atlantic region. Cloud radiative forcing, sea ice concentrations, and surface temperatures are interrelated in this region, and may be forced by the same physical mechanism. The response of Arctic clouds and surface radiative properties is examined using the polar version of the Weather Research and Forecasting (WRF) regional model over the Laptev Sea. WRF is run for four Septembers and Octobers with anomalously low and high sea ice concentrations. Differences in the surface radiative forcing, cloud radiative forcing, cloud properties and the surface heat budget are examined for the composite low and high years. In both months, there are more clouds during low sea ice years. WRF produces more low-level liquid cloud amount during years without sea ice. The increase in clouds during low sea ice years corresponds with an increase in downwelling longwave radiation, and hence longwave cloud radiative forcing. Increases in downwelling longwave radiation during low sea ice years are canceled by the increased amount of upwelling longwave radiation, which is a result of warmer surface skin temperatures. In September, the decrease in surface albedo associated with sea ice retreat/melt results in an increased net surface radiation during low sea ice years. In October, the changes in net surface radiation are not statistically significant. After the Arctic solar night begins, during times with no sea ice, large latent and sensible heat upward surface fluxes aids in the deepening of the boundary layer and preventing the formation of the typical Arctic inversion. In WRF, the increases in cloud water liquid content and downwelling longwave radiation, in low sea ice years, seems to be a result of increased open water, while the changes in the boundary layer are the result of changes in the surface radiative fluxes.
Download or read book Arctic Climate Change written by Peter Lemke and published by Springer Science & Business Media. This book was released on 2011-11-22 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic is now experiencing some of the most rapid and severe climate change on earth. Over the next 100 years, climate change is expected to accelerate, contributing to major physical, ecological, social, and economic changes, many of which have already begun. Changes in arctic climate will also affect the rest of the world through increased global warming and rising sea levels. The volume addresses the following major topics: - Research results in observing aspects of the Arctic climate system and its processes across a range of time and space scales - Representation of cryospheric, atmospheric, and oceanic processes in models, including simulation of their interaction with coupled models - Our understanding of the role of the Arctic in the global climate system, its response to large-scale climate variations, and the processes involved.
Download or read book Amplified Climate Changes in the Arctic written by Manfred Wendisch and published by . This book was released on 2013 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: A presentation given at the regular plenary session of the Academy of Sciences of Saxony in Leipzig (Germany) on October 12, 2012, is thoroughly summarized. Additional aspects important to the theme but not covered in the talk have been added to complete the text. The characteristic conditions and processes leading to the so-called Arctic amplification are outlined. The phenomenon of Arctic amplification comprises an enhanced variability and amplified increase of the near-surface air temperature in the Arctic in comparison to the average near-surface warming at lower latitudes. Observations and simulations show the magnitude of the observed Arctic near-surface air temperature increase is more than double the air temperature increase at lower latitudes. To illustrate the phenomenon of Arctic amplification, several examples of observed Arctic near-surface air temperature increases are presented. In general, Arctic amplification also implies serious Arctic climate changes other than near-surface air temperature, such as the dramatic summer melting of Arctic Sea ice and the Greenland ice sheet, and the decrease of snow cover and surface albedo of the Greenland ice sheet. Numerous reasons for the Arctic climate changes are discussed; the direct and indirect surface albedo feedback and the related increase of near-surface water vapor and cloudiness, meridional heat and water vapor transports in the atmosphere and ocean, and increased soot amounts in both the atmosphere and snow/ice surfaces. The special role of low-level clouds under Arctic conditions (low Sun, polar day and night, high surface albedo) for the self-enforcing amplification processes is described. In particular, the impact of ice in Arctic mixed-phase clouds on the cloud radiative forcing is investigated. Methods of ice detection in mixed-phase Arctic clouds are presented along with verification examples.
Download or read book Thriving on Our Changing Planet A Decadal Strategy for Earth Observation from Space written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-06-18 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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: A Decadal Strategy for Earth Observation from Space (National Academies Press, 2018) provides detailed guidance on how relevant federal agencies can ensure that the United States receives the maximum benefit from its investments in Earth observations from space, while operating within realistic cost constraints. This short booklet, designed to be accessible to the general public, provides a summary of the key ideas and recommendations from the full decadal survey report.
Download or read book Arctic Cloud Simulations with the Mesoscale Model Gesima written by Jiaxiong Pi and published by . This book was released on 2001 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent climate modeling results highlighted the Arctic as a region of importance and vulnerability to global climate change. The ability to understand and simulate cloud and radiative properties is of central importance to our understanding of the Arctic climate system. The mesoscale model GESIMA is used to simulate microphysical properties and radiation process of Arctic clouds. For an idealized case, the cloud module is tested in a vertical column to study the importance of individual microphysical processes and the model's sensitivity to aerosol number concentration. For the three-dimensional simulations, the comparisons between simulations and observations show that the GESIMA model can capture the main processes in the clouds. For two aerosol scenarios, the simulation results show that the anthropogenic aerosol can alter microphysical properties of Arctic clouds, and consequently surface precipitation and radiation budget. The three-dimensional GESIMA model is sensitive to depositional nucleation process. These different parameterizations of the process have a significant effect on Ice Water Path (IWP), surface precipitation and radiation at the top of atmosphere.
Download or read book Physics and Chemistry of the Arctic Atmosphere written by Alexander Kokhanovsky and published by Springer Nature. This book was released on 2020-01-29 with total page 723 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents current knowledge on chemistry and physics of Arctic atmosphere. Special attention is given to studies of the Arctic haze phenomenon, Arctic tropospheric clouds, Arctic fog, polar stratospheric and mesospheric clouds, atmospheric dynamics, thermodynamics and radiative transfer as related to the polar environment. The atmosphere-cryosphere feedbacks and atmospheric remote sensing techniques are presented in detail. The problems of climate change in the Arctic are also addressed.
Download or read book Radiative Effects of Arctic Clouds in Observations and Models written by Anne Sledd and published by . This book was released on 2021 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Arctic Clouds from Model Simulations and Long term Observations at Barrow Alaska written by Ming Zhao and published by . This book was released on 2012 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic is a region that is very sensitive to global climate change while also experiencing significant changes in its surface air temperature, sea-ice cover, atmospheric circulation, precipitation, snowfall, biogeochemical cycling, and land surface. Although previous studies have shown that the arctic clouds play an important role in the arctic climate changes, the arctic clouds are poorly understood and simulated in climate model due to limited observations. Furthermore, most of the studies were based on short-term experiments and typically only cover the warm seasons, which do not provide a full understanding of the seasonal cycle of arctic clouds. To address the above concerns and to improve our understanding of arctic clouds, six years of observational and retrieval data from 1999 to 2004 at the Atmospheric Radiation Management (ARM) Climate Research Facility (ACRF) North Slope of Alaska (NSA) Barrow site are used to understand the arctic clouds and related radiative processes. In particular, we focus on the liquid-ice mass partition in the mixed-phase cloud layer. Statistical results show that aerosol type and concentration are important factors that impact the mixed-phase stratus (MPS) cloud microphysical properties: liquid water path (LWP) and liquid water fraction (LWF) decrease with the increase of cloud condensation nuclei (CCN) number concentration; the high dust loading and dust occurrence in the spring are possible reasons for the much lower LWF than the other seasons. The importance of liquid-ice mass partition on surface radiation budgets was analyzed by comparing cloud longwave radiative forcings under the same LWP but different ice water path (IWP) ranges. Results show the ice phase enhance the surface cloud longwave (LW) forcing by 8~9 W m−2 in the moderately thin MPS. This result provides an observational evidence on the aerosol glaciation effect in the moderately thin MPS, which is largely unknown so far. The above new insights are important to guide the model parameterizations of liquid-ice mass partition in arctic mixed-phase clouds, and are served as a test bed to cloud models and cloud microphysical schemes. The observational data between 1999 and 2007 are used to assess the performance of the European Center for Medium-Range Weather Forecasts (ECMWF) model in the Arctic region. The ECMWF model-simulated near-surface humidity had seasonal dependent biases as large as 20%, while also experiencing difficulty representing boundary layer (BL) temperature inversion height and strength during the transition seasons. Although the ECMWF model captured the seasonal variation of surface heat fluxes, it had sensible heat flux biases over 20 W m−2 in most of the cold months. Furthermore, even though the model captured the general seasonal variations of low-level cloud fraction (LCF) and LWP, it still overestimated the LCF by 20% or more and underestimated the LWP over 50% in the cold season. On average, the ECMWF model underestimated LWP by ~30 g m−2 but more accurately predicted ice water path for BL clouds. For BL mixed-phase clouds, the model predicted water-ice mass partition was significantly lower than the observations, largely due to the temperature dependence of water-ice mass partition used in the model. The new cloud and BL schemes of the ECMWF model that were implemented after 2003 only resulted in minor improvements in BL cloud simulations in summer. These results indicate that significant improvements in cold season BL and mixed-phase cloud processes in the model are needed. In this study, single-layer MPS clouds were simulated by the Weather Research and Forecasting (WRF) model under different microphysical schemes and different ice nuclei (IN) number concentrations. Results show that by using proper IN concentration, the WRF model incorporated with Morrison microphysical scheme can reasonably capture the observed seasonal differences in temperature dependent liquid-ice mass partition. However, WRF simulations underestimate both LWP and IWP indicating its deficiency in capturing the radiative impacts of arctic MPS clouds.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global Energy and Water Cycles written by K. A. Browning and published by Cambridge University Press. This book was released on 1999-02 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive treatment of models and processes related to water fluxes for meteorologists, hydrologists and oceanographers.
Download or read book Impact of the Ice Phase on a Mesoscale Convective System written by and published by . This book was released on 1991 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study attempts to provide further understanding of the effect of the ice phase on cloud ensemble features which are useful for improving GCM cumulus parameterization. In addition, cloud model results are used to diagnose the radiative properties of anvils in order to assess cloud/radiation interaction and its feedback on the larger-scale climate for the future work. The heat, moisture and mass budget analyses of a simulated squall line system indicate that, at least for this type of system, the inclusion of the ice phase in the microphysics does not considerably change the net cloud heating and drying effects and the feedback on the large-scale motion. Nonetheless, its impact on the radiative properties of clouds significantly influences not only the squall line system itself, but also the larger-scale circulation due to the favorable stratification for long-lasting anvil clouds. The water budget suggests a simple methodology to parameterize the microphysical effect without considering it as a model physics module. Further application of the water budget might also be used to parameterize the cloud transport of condensates in the anvil cloud region, which allows the GCM columns to interact with each other. The findings of this study suggest that the ice phase could be ignored in the cloud parameterization in order to save significant amounts of computational resources and to simplify the model physics. More scientific effort should, however, be focused on the effect of the ice phase to further explore cloud feedback on the large-scale climate through the radiative process. The cloud/radiation interaction and its feedback on the larger-scale climate will be addressed in a companion study by coupling the radiative transfer model with the cloud model. 19 refs., 13 figs.
Download or read book Observing and Modeling Arctic Clouds written by Elin McIlhattan and published by . This book was released on 2019 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clouds are the primary modulator of radiation and moisture received by the Arctic surface. Long term, large scale, and detailed observations of Arctic clouds are required to connect particular cloud macro- and microphysical characteristics to their influence on the varied surfaces of the Arctic. Constraining that influence is key to accurate projections of future climate, particularly sea level rise. Prior to the launch of CloudSat and CALIPSO in 2006, Arctic cloud observations were limited in either time (field campaigns), space (individual research stations), or sensitivity (passive satellites). CloudSat's Cloud Profiling Radar (CPR) and CALIPSO's Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) have provided detailed information on the location, phase, and vertical structure of Arctic clouds. This study leverages data from these two instruments to explore the connections between Arctic cloud phase, precipitation, and surface radiation. First, the connection between cloud phase and precipitation is documented over the Greenland Ice Sheet (GIS). Partitioning snowfall observed over the GIS into two regimes --- snowfall produced by ice-phase clouds and snowfall produced by Arctic mixed-phase clouds --- reveals that the two regimes are distinct beyond the cloud phase that defines them, including differing seasonal and regional frequency, snowfall rates, geometric cloud depth, and air mass origins. Next, Arctic cloud representation is compared between two versions of the Community Earth System Model (CESM), with CloudSat and CALIPSO observations used to provide physically reasonable benchmarks. The updated version of CESM has a markedly different mean state than the previous version, having addressed a known bias in Arctic mixed-phase clouds. Finally, the connection to surface radiation is examined using the Cloud Impact on Surface Radiation Ratio (CISRR). CISRR shows that over the icy surfaces of the Arctic, on average the warming effect of a cloud is at minimum twice as strong as its cooling effect.
Download or read book Arctic Climate System Study ACSYS written by and published by . This book was released on 1994 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Thin Midlevel Ice Clouds in the Arctic Using Calipso Data and Radiative Transfer Modeling written by Vinay Kumar Kayetha and published by . This book was released on 2015 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this research we investigate the global occurrence and properties of optically thin midlevel ice clouds. These clouds are difficult to detect with passive radiometric techniques and are under-represented in current studies. We use the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data set to identify thin midlevel ice clouds and determine their global occurrence and distribution. For the first time, we find that the global mean occurrence of these clouds is at least 4.5%, being at least 7.3% of all the tropospheric clouds detected at a horizontal scale of 10 km. Seasonally, these clouds are found most commonly in the polar regions. These clouds occur most commonly in the Arctic in winter and least commonly in the summer. In winter these clouds can occur up to 19% of the time. The occurrence of these clouds decreases with increasing spatial scale and are most commonly found at spatial scales of 25 km or less. We found five large distinct clouds over the Arctic and investigated them for their meteorological conditions and radiative effects. These thin midlevel ice clouds are formed along the frontal zones in weakly ascending air masses. Our model simulations show that thin midlevel ice clouds have a net warming effect on the surface of 23-48 W/m2. We conclude that these clouds have a significant impact on the radiation budget in Arctic winters. Our study highlights the importance of active satellite-based remote sensing in globally detecting and characterizing optically thin clouds. Our estimates of occurrence and fraction of clouds represents a lower bound, as these clouds can be obscured by optically thicker clouds. The volume of measurements provided by the satellite allowed us to identify a small but consistent set of large clouds with which we could conduct a contemporary radiative analysis. These findings can be used to improve the representation of clouds and their impacts in regional and global climate models.
Download or read book The Arctic Climate System written by Mark C. Serreze and published by Cambridge University Press. This book was released on 2005-10-13 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic can be viewed as an integrated system, characterised by intimate couplings between its atmosphere, ocean and land, linked in turn to the larger global system. This comprehensive, up-to-date assessment begins with an outline of early Arctic exploration and the growth of modern research. Using an integrated systems approach, subsequent chapters examine the atmospheric heat budget and circulation, the surface energy budget, the hydrologic cycle and interactions between the ocean, atmosphere and sea ice cover. Reviews of recent directions in numerical modelling and the characteristics of past Arctic climates set the stage for detailed discussion of recent climate variability and trends, and projected future states. Throughout, satellite remote sensing data and results from recent major field programs are used to illustrate key processes. The Arctic Climate System provides a comprehensive and accessible overview of the subject for researchers and advanced students in a wide range of disciplines.
Download or read book Assessment of Climate Variability of the Greenland Ice Sheet Integration of in Situ and Satellite Data written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-10-25 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed research involves the application of multispectral satellite data in combination with ground truth measurements to monitor surface properties of the Greenland Ice Sheet which are essential for describing the energy and mass of the ice sheet. Several key components of the energy balance are parameterized using satellite data and in situ measurements. The analysis will be done for a ten year time period in order to get statistics on the seasonal and interannual variations of the surface processes and the climatology. Our goal is to investigate to what accuracy and over what geographic areas large scale snow properties and radiative fluxes can be derived based upon a combination of available remote sensing and meteorological data sets. Operational satellite sensors are calibrated based on ground measurements and atmospheric modeling prior to large scale analysis to ensure the quality of the satellite data. Further, several satellite sensors of different spatial and spectral resolution are intercompared to access the parameter accuracy. Proposed parameterization schemes to derive key component of the energy balance from satellite data are validated. For the understanding of the surface processes a field program was designed to collect information on spectral albedo, specular reflectance, soot content, grain size and the physical properties of different snow types. Further, the radiative and turbulent fluxes at the ice/snow surface are monitored for the parameterization and interpretation of the satellite data. The expected results include several baseline data sets of albedo, surface temperature, radiative fluxes, and different snow types of the entire Greenland Ice Sheet. These climatological data sets will be of potential use for climate sensitivity studies in the context of future climate change. Steffen, K. and Abdalati, W. and Stroeve, J. and Key, J. Unspecified Center NAGW-2158
Download or read book Mixed Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
