scholarly journals What rainfall rates are most important to wet removal of different aerosol types?

2021 ◽  
Vol 21 (22) ◽  
pp. 16797-16816
Author(s):  
Yong Wang ◽  
Wenwen Xia ◽  
Guang J. Zhang
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Deep Convection ◽  
Global Climate Models ◽  
Precipitation Frequency ◽  
Light Rain ◽  
Community Atmosphere Model ◽  
Novel Approach ◽  
Aerosol Types ◽  
Wet Removal

Abstract. Both frequency and intensity of rainfall affect aerosol wet deposition. With a stochastic deep convection scheme implemented into two state-of-the-art global climate models (GCMs), a recent study found that aerosol burdens are increased globally by reduced climatological mean wet removal of aerosols due to suppressed light rain. Motivated by their work, a novel approach is developed in this study to detect what rainfall rates are most efficient for wet removal (scavenging amount mode) of different aerosol species of different sizes in GCMs and applied to the National Center for Atmospheric Research Community Atmosphere Model version 5 (CAM5) with and without the stochastic convection cases. Results show that in the standard CAM5, no obvious differences in the scavenging amount mode are found among different aerosol types. However, the scavenging amount modes differ in the Aitken, accumulation and coarse modes, showing around 10–12, 8–9 and 7–8 mm d−1, respectively, over the tropics. As latitude increases poleward, the scavenging amount mode in each aerosol mode is decreased substantially. The scavenging amount mode is generally smaller over land than over ocean. With stochastic convection, the scavenging amount mode for all aerosol species in each mode is systematically increased, which is the most prominent along the Intertropical Convergence Zone, exceeding 20 mm d−1 for small particles. The scavenging amount modes in the two cases are both smaller than individual rainfall rates associated with the most accumulated rain (rainfall amount mode), further implying precipitation frequency is more important than precipitation intensity for aerosol wet removal. The notion of the scavenging amount mode can be applied to other GCMs to better understand the relation between rainfall and aerosol wet scavenging, which is important to better simulate aerosols.

scholarly journals What rainfall rates are most important to wet removal of different aerosol types?

2021 ◽  
Author(s):  
Yong Wang ◽  
Wenwen Xia ◽  
Guang J. Zhang
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
Convection Scheme ◽  
Precipitation Frequency ◽  
Light Rain ◽  
Aerosol Types ◽  
Wet Removal

Abstract. Both frequency and intensity of rainfall affect aerosol wet deposition. With a stochastic deep convection scheme implemented into two state-of-the-art global climate models (GCMs), a recent study found that aerosol burdens are increased globally by reduced climatological mean wet removal of aerosols due to suppressed light rain. Motivated by their work, a novel approach is developed in this study to detect what rainfall rates are most efficient for wet removal (scavenging amount mode) of different aerosol species in different sizes in GCMs and applied to the National Center for Atmospheric Research Community Atmosphere Model version 5 (CAM5) with and without the stochastic convection cases. Results show that in the standard CAM5, no obvious differences in the scavenging amount mode are found among different aerosol types. However, the scavenging amount modes differ in the Aitken, accumulation and coarse modes showing around 10-12, 8-9, and 7-8 mm d−1, respectively over the tropics. As latitude increases poleward, the scavenging amount mode in each aerosol mode is decreased substantially. The scavenging amount mode is generally smaller over land than over ocean. With stochastic convection, the scavenging amount mode for all aerosol species in each mode is systematically increased, which is the most prominent along the Intertropical Convergence Zone exceeding 20 mm d−1 for small particles. Regardless of whether the stochastic convection scheme is used, convective precipitation has higher efficiency in removing aerosols than large-scale precipitation over the globe even though convection is infrequent over high-latitudes. The scavenging amount modes in the two cases are both smaller than individual rainfall rates associated with the most accumulated rain (rainfall amount mode), further implying precipitation frequency is more important than precipitation intensity for aerosol wet removal. The notion of the scavenging amount mode can be applied to other GCMs to better understand the relation between rainfall and aerosol wet scavenging, which is important to better simulating aerosols.

scholarly journals Regional Perspective on Mechanisms for Tropical Precipitation Frequency and Intensity under Global Warming

2012 ◽  
Vol 25 (24) ◽  
pp. 8487-8501 ◽  
Author(s):  
Chao-An Chen ◽  
Chia Chou ◽  
Cheng-Ta Chen
Keyword(s):  
Global Warming ◽  
Climate Models ◽  
Global Climate ◽  
Longwave Radiation ◽  
Heavy Precipitation ◽  
Point Of View ◽  
Global Climate Models ◽  
Main Process ◽  
Precipitation Frequency ◽  
Horizontal Advection

Abstract From a global point of view, a shift toward more intense precipitation is often found in observations and global warming simulations. However, similar to changes in mean precipitation, these changes associated with precipitation characters, such as intensity and frequency, should vary with space. Based on the classification of the subregions for the tropics in Chou et al., changes in precipitation frequency and intensity and their association with changes in mean precipitation are analyzed on a regional basis in 10 coupled global climate models. Furthermore, mechanisms for these changes are also examined, via the thermodynamic and dynamic contributions. In general, the increase (decrease) of mean precipitation is mainly attributed to increases (decreases) in the frequency and intensity of almost all strengths of precipitation: that is, light to heavy precipitation. The thermodynamic contribution, which is associated with increased water vapor, is positive to both precipitation frequency and intensity, particularly for precipitation extremes, and varies little with space. On the other hand, the dynamic contribution, which is related to changes in the tropical circulation, is the main process for inducing the spatial variation of changes in precipitation frequency and intensity. Among mechanisms that induce the dynamic contribution, the rich-get-richer mechanism (the dynamic part), ocean feedback, and warm horizontal advection increase precipitation frequency and intensity, while the upped-ante mechanism, the deepening of convection, longwave radiation cooling, and cold horizontal advection tend to reduce precipitation frequency and intensity.

scholarly journals Southern Ocean deep convection in global climate models: A driver for variability of subpolar gyres and Drake Passage transport on decadal timescales

2016 ◽  
Vol 121 (6) ◽  
pp. 3905-3925 ◽  
Author(s):  
Erik Behrens ◽  
Graham Rickard ◽  
Olaf Morgenstern ◽  
Torge Martin ◽  
Annette Osprey ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Climate Models ◽  
Global Climate ◽  
Deep Convection ◽  
Drake Passage ◽  
Global Climate Models

How Often Does It Rain?

2006 ◽  
Vol 19 (6) ◽  
pp. 916-934 ◽  
Author(s):  
Ying Sun ◽  
Susan Solomon ◽  
Aiguo Dai ◽  
Robert W. Portmann
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Precipitation Amount ◽  
Heavy Precipitation ◽  
Global Climate Models ◽  
Annual Precipitation ◽  
Precipitation Frequency ◽  
Daily Precipitation Data ◽  
Precipitation Total ◽  
Rainy Days

Abstract Daily precipitation data from worldwide stations and gridded analyses and from 18 coupled global climate models are used to evaluate the models' performance in simulating the precipitation frequency, intensity, and the number of rainy days contributing to most (i.e., 67%) of the annual precipitation total. Although the models examined here are able to simulate the land precipitation amount well, most of them are unable to reproduce the spatial patterns of the precipitation frequency and intensity. For light precipitation (1–10 mm day−1), most models overestimate the frequency but produce patterns of the intensity that are in broad agreement with observations. In contrast, for heavy precipitation (>10 mm day−1), most models considerably underestimate the intensity but simulate the frequency relatively well. The average number of rainy days contributing to most of the annual precipitation is a simple index that captures the combined effects of precipitation frequency and intensity on the water supply. The different measures of precipitation characteristics examined in this paper reveal region-to-region differences in the observations and models of relevance for climate variability, water resources, and climate change.

scholarly journals California Wintertime Precipitation Bias in Regional and Global Climate Models

2010 ◽  
Vol 49 (10) ◽  
pp. 2147-2158 ◽  
Author(s):  
Peter Caldwell
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Global Climate ◽  
Regional Climate ◽  
Regional Climate Models ◽  
General Circulation Models ◽  
Global Climate Models ◽  
Model Resolution ◽  
Grid Spacing ◽  
Precipitation Frequency

Abstract In this paper, wintertime precipitation from a variety of observational datasets, regional climate models (RCMs), and general circulation models (GCMs) is averaged over the state of California and compared. Several averaging methodologies are considered and all are found to give similar values when the model grid spacing is less than 3°. This suggests that California is a reasonable size for regional intercomparisons using modern GCMs. Results show that reanalysis-forced RCMs tend to significantly overpredict California precipitation. This appears to be due mainly to the overprediction of extreme events; RCM precipitation frequency is generally underpredicted. Overprediction is also reflected in wintertime precipitation variability, which tends to be too high for RCMs on both daily and interannual scales. Wintertime precipitation in most (but not all) GCMs is underestimated. This is in contrast to previous studies based on global blended gauge–satellite observations, which are shown here to underestimate precipitation relative to higher-resolution gauge-only datasets. Several GCMs provide reasonable daily precipitation distributions, a trait that does not seem to be tied to model resolution. The GCM daily and interannual variabilities are generally underpredicted.

scholarly journals Multiscale Simulation of Precipitation over East Asia by Variable Resolution CAM-MPAS

2021 ◽  
Author(s):  
Yuan Liang ◽  
Ben Yang ◽  
Minghuai Wang ◽  
Jianping Tang ◽  
Koichi Sakaguchi ◽  
...  
Keyword(s):  
East Asia ◽  
Climate Models ◽  
Global Climate ◽  
Regional Scale ◽  
Multiscale Simulation ◽  
Global Climate Models ◽  
Tibet Plateau ◽  
Variable Resolution ◽  
Precipitation Simulation ◽  
Community Atmosphere Model

<p>Traditional global climate models (GCMs) with coarse uniform resolution (UR) usually have deficiency in simulating realistic results at regional scale, while experimental global high-resolution models show benefits but also raise much computational burden. In recent years, variable resolution (VR) models with unstructured mesh are found to provide comparable results at regional scale and require less computational resources. In this study, the variable resolution CAM-MPAS model with the MPAS (Model for Prediction Across Scales) dynamical core coupled with CAM5 (Community Atmosphere Model Version 5) physics package is used to evaluate the effect of 30 km regional refinement over East Asia on the precipitation simulation. Our results show that the CAM-MPAS model can reasonably reproduce the annual and seasonal precipitation over East Asia, and the MPAS-VR simulation shows reduced mean bias and improvements in seasonal cycle, intensity distribution, and interannual variation compared with the low resolution MPAS-UR simulation. Furthermore, the major contribution to the improvements over the Tibet Plateau in the MPAS-VR experiment comes from the increase of the grid spacing rather than the terrain resolution.</p>

scholarly journals Impacts of Vertical Structure of Convection in Global Warming: The Role of Shallow Convection

2016 ◽  
Vol 29 (12) ◽  
pp. 4665-4684 ◽  
Author(s):  
Chao-An Chen ◽  
Jia-Yuh Yu ◽  
Chia Chou
Keyword(s):  
Global Warming ◽  
Climate Models ◽  
Global Climate ◽  
Deep Convection ◽  
Atmospheric Stability ◽  
Detailed Examination ◽  
Global Climate Models ◽  
Shallow Convection ◽  
Tropical Circulation ◽  
Heavy Structure

Abstract Global-warming-induced changes in regional tropical precipitation are usually associated with changes in the tropical circulation, which is a dynamic contribution. This study focuses on the mechanisms of the dynamic contribution that is related to the partition of shallow convection in tropical convection. To understand changes in tropical circulation and its associated mechanisms, 32 coupled global climate models from CMIP3 and CMIP5 were investigated. The study regions are convection zones with positive precipitation anomalies, where both enhanced and reduced ascending motions are found. Under global warming, an upward-shift structure of ascending motion is observed in the entire domain, implying a deepening of convection and a more stable atmosphere, which leads to a weakening of the tropical circulation. In a more detailed examination, areas with enhanced (weakened) ascending motion are associated with more (less) import of moist static energy by a climatologically bottom-heavy (top heavy) structure of vertical velocity, which is similar to a “rich get richer” mechanism. In a warmer climate, different climatological vertical profiles tend to induce different changes in atmospheric stability: the bottom-heavy (top heavy) structure brings a more (less) unstable condition and is favorable (unfavorable) to the strengthening of the convective circulation. The bottom-heavy structure is associated with shallow convection, while the top-heavy structure is usually related to deep convection. This study suggests a hypothesis and a possible linkage for projecting and understanding future circulation change from the current climate: shallow convection will tend to strengthen tropical circulation and enhance upward motion in a future warmer climate.

scholarly journals Overview of the New Version 3 NASA Micro-Pulse Lidar Network (MPLNET) Automatic Precipitation Detection Algorithm

2019 ◽  
Vol 12 (1) ◽  
pp. 71 ◽  
Author(s):  
Simone Lolli ◽  
Gemine Vivone ◽  
Jasper R. Lewis ◽  
Michaël Sicard ◽  
Ellsworth J. Welton ◽  
...  
Keyword(s):  
Climate Models ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Heavy Rain ◽  
Detection Algorithm ◽  
Processing Technique ◽  
Global Climate Models ◽  
Mitigation Strategies ◽  
Image Processing Technique ◽  
Light Rain

Precipitation modifies atmospheric column thermodynamics through the process of evaporation and serves as a proxy for latent heat modulation. For this reason, a correct precipitation parameterization (especially for low-intensity precipitation) within global scale models is crucial. In addition to improving our modeling of the hydrological cycle, this will reduce the associated uncertainty of global climate models in correctly forecasting future scenarios, and will enable the application of mitigation strategies. In this manuscript we present a proof of concept algorithm to automatically detect precipitation from lidar measurements obtained from the National Aeronautics and Space Administration Micropulse lidar network (MPLNET). The algorithm, once tested and validated against other remote sensing instruments, will be operationally implemented into the network to deliver a near real time (latency <1.5 h) rain masking variable that will be publicly available on MPLNET website as part of the new Version 3 data products. The methodology, based on an image processing technique, detects only light precipitation events (defined by intensity and duration) such as light rain, drizzle, and virga. During heavy rain events, the lidar signal is completely extinguished after a few meters in the precipitation or it is unusable because of water accumulated on the receiver optics. Results from the algorithm, in addition to filling a gap in light rain, drizzle, and virga detection by radars, are of particular interest for the scientific community as they help to fully characterize the aerosol cycle, from emission to deposition, as precipitation is a crucial meteorological phenomenon accelerating atmospheric aerosol removal through the scavenging effect. Algorithm results will also help the understanding of long term aerosol–cloud interactions, exploiting the multi-year database from several MPLNET permanent observational sites across the globe. The algorithm is also applicable to other lidar and/or ceilometer network infrastructures in the framework of the Global Aerosol Watch (GAW) aerosol lidar observation network (GALION).

scholarly journals Contribution of Atlantic and Pacific Multidecadal Variability to Twentieth-Century Temperature Changes

2017 ◽  
Vol 30 (16) ◽  
pp. 6279-6295 ◽  
Author(s):  
Martin B. Stolpe ◽  
Iselin Medhaug ◽  
Reto Knutti
Keyword(s):  
Twentieth Century ◽  
Climate Models ◽  
Global Climate ◽  
Internal Variability ◽  
Global Climate Models ◽  
Multidecadal Variability ◽  
Temperature Changes ◽  
Cooling Period ◽  
Novel Approach ◽  
Late Twentieth

Recent studies have suggested that significant parts of the observed warming in the early and the late twentieth century were caused by multidecadal internal variability centered in the Atlantic and Pacific Oceans. Here, a novel approach is used that searches for segments of unforced preindustrial control simulations from global climate models that best match the observed Atlantic and Pacific multidecadal variability (AMV and PMV, respectively). In this way, estimates of the influence of AMV and PMV on global temperature that are consistent both spatially and across variables are made. Combined Atlantic and Pacific internal variability impacts the global surface temperatures by up to 0.15°C from peak-to-peak on multidecadal time scales. Internal variability contributed to the warming between the 1920s and 1940s, the subsequent cooling period, and the warming since then. However, variations in the rate of warming still remain after removing the influence of internal variability associated with AMV and PMV on the global temperatures. During most of the twentieth century, AMV dominates over PMV for the multidecadal internal variability imprint on global and Northern Hemisphere temperatures. Less than 10% of the observed global warming during the second half of the twentieth century is caused by internal variability in these two ocean basins, reinforcing the attribution of most of the observed warming to anthropogenic forcings.

scholarly journals Enhanced warming of seasonal cold extremes relative to the mean in the Northern Hemisphere extratropics

2019 ◽  
Author(s):  
Mia H. Gross ◽  
Markus G. Donat ◽  
Lisa V. Alexander ◽  
Steven C. Sherwood
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Northern Eurasia ◽  
Cold Temperatures ◽  
Physical Mechanisms ◽  
Novel Approach ◽  
Late 21St Century ◽  
Cold Extremes

Abstract. Cold extremes are anticipated to warm at a faster rate than both hot extremes and average temperatures for much of the Northern Hemisphere. The consequences of warming cold extremes can affect numerous sectors, including human health, tourism and various ecosystems that are sensitive to cold temperatures. Using a selection of Global Climate Models, this paper explores the enhanced warming of seasonal cold extremes relative to seasonal mean temperatures in the Northern Hemisphere extratropics. The potentially driving physical mechanisms are investigated by assessing conditions on the day, or prior to, when the cold extreme occurs to understand how the different environmental fields are related. During winter months, North America, Europe and much of Eurasia show enhanced warming of cold extremes projected for the late 21st century, compared to the mid-20th century. This is shown to be largely driven by reductions in cold air temperature advection, suggested as a likely consequence of Arctic amplification. In spring and autumn, cold extremes are expected to warm faster than average temperatures for most of the Northern Hemisphere mid- to high-latitudes, particularly Alaska, northern Canada and northern Eurasia. In the shoulder seasons, projected decreases in snow cover and associated reductions in surface albedo are suggested as the largest contributor affecting the accelerated rates of warming in cold extremes. This study uses a novel approach to examine the day in which the extreme occurs to improve our understanding of the environmental conditions that contribute to the accelerated warming of cold extremes relative to mean temperatures.

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