The Importance of Radiative Feedbacks in Tropical Cyclogenesis in Idealized Simulations

2021 ◽  
Author(s):  
Allison Wing
Keyword(s):  
Water Vapor ◽  
Random Noise ◽  
Tropical Cyclogenesis ◽  
Radiative Cooling ◽  
Ice Clouds ◽  
Forecast Models ◽  
Cloud Radiative Effects ◽  
Radiative Feedbacks ◽  
The Impact

<p>Interactions between clouds, radiation, and circulations are fundamental to tropical climate, but until recently, the impact of these interactions on tropical cyclones (TCs) has been relatively unexplored. Simulations of rotating radiative-convective equilibrium confirm that radiative feedbacks are important for spontaneous TC genesis (in which a TC is allowed to form from random noise). While not strictly necessary, radiative feedbacks significantly accelerate TC genesis and especially contribute in the early stages of genesis. These radiative feedbacks arise from interactions between spatially and temporally varying radiative cooling (driven by the dependence of radiative cooling rate on clouds and water vapor) and the developing tropical cyclone (the circulation of which shapes the structure of clouds and water vapor).  However, TCs in nature are generally observed to form from pre-existing disturbances, calling into question whether radiative feedbacks play a significant role.</p><p>Here, I investigate the importance of radiative feedbacks in TC genesis and the mechanisms underlying their influence in a set of idealized cloud-resolving simulations in which a TC is allowed to develop after initialization from a mesoscale warm, saturated bubble on an f-plane, in an otherwise quiescent and moist neutral environment. TC genesis is delayed by a factor of two or three when radiative feedbacks are removed by prescribing a fixed cooling profile or spatially homogenizing the model-calculated cooling profiles. Further analysis and additional mechanism denial experiments pinpoint the longwave radiative feedback contributed by ice clouds as the strongest influence. These results are consistent with recently published case study simulations in which cloud-radiative effects accelerate TC formation and intensification in realistic scenarios. The important takeaway from the results presented here is that that cloud-longwave radiative feedbacks have a profound impact on TC genesis in a hierarchy of model simulations. Improving the representation of cloud-radiative feedbacks in forecast models therefore has the potential to yield critical advancements in TC prediction.</p>

Drought spatiotemporal propagation via land feedbacks

2021 ◽  
Author(s):  
Diego G. Miralles ◽  
Dominik L. Schumacher ◽  
Jessica Keune ◽  
Paul A. Dirmeyer
Keyword(s):  
Soil Moisture ◽  
Water Vapor ◽  
Mitigation Strategies ◽  
Soil Drought ◽  
The Usa ◽  
Forecast Models ◽  
Atmospheric Feedbacks ◽  
Dry Out ◽  
Water And Food Security ◽  
The Impact

<p>The predicted increase in drought occurrence and intensity will pose serious threats to global future water and food security. This was hinted by several historically unprecedented droughts over the last two decades, taking place in Europe, Australia, Amazonia or the USA. It has been hypothesised that the strength of these events responded to self-reinforcement processes related to land–atmospheric feedbacks: as rainfall deficits dry out soil and vegetation, the evaporation of land water is reduced, then the local air becomes too dry to yield rainfall, which further enhances drought conditions. Despite the 'local' nature of these feedbacks, their consequences can be remote, as downwind regions may rely on evaporated water transported by winds from drought-affected locations. Following this rationale, droughts may not only self-reinforce locally, due to land atmospheric feedbacks, but <em>self-propagate</em> in the downwind direction, always conditioned on atmospheric circulation. This propagation is not only meteorological but relies on soil moisture drought, and may lead to a downwind cascading of impacts on water resources. However, a global capacity to observe these processes is lacking, and thus our knowledge of how droughts start and evolve, and how this may change as climate changes, remains limited. Furthermore, climate and forecast models are still immature when it comes to representing the influences of land on rainfall.</p><p>Here, the largest global drought events are studied to unravel the role of land–atmosphere feedbacks during the spatiotemporal propagation of these events. We based our study on satellite and reanalysis records of soil moisture, evaporation, air humidity, winds and precipitation, in combination with a Lagrangian framework that can map water vapor trajectories and explore multi-dimensional feedbacks. We estimate the reduction in precipitation in the direction of drought propagation that is caused by the upwind soil moisture drought, and isolate this effect from the influence of potential evaporation and circulation changes. By doing so, the downwind lack of precipitation caused by upwind soil drought via water vapor deficits, and hence the impact of drought self-propagation, is determined. We show that droughts occurring in dryland regions are particularly prone to self-propagate, as evaporation there tends to respond strongly to enhanced soil stress and precipitation is frequently convective. This kind of knowledge may be used to improve climate and forecast models and can be exploited to develop geo-engineering mitigation strategies to help prevent drought events from aggravating during their early stages.</p>

Application of equal loudness contour in assessing the impact of random noise: Case study in continuous positive airway pressure systems with helmet

2014 ◽  
Vol 76 ◽  
pp. 100-106
Author(s):  
Francisco Fernández Zacarías ◽  
Ricardo Hernández Molina ◽  
José Luis Cueto Ancela ◽  
Simón Lubián López ◽  
Isabel Benavente Fernández
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Random Noise ◽  
The Impact

scholarly journals A water vapor modulated aerosol impact on ice crystal size

2017 ◽  
Author(s):  
Bin Zhao ◽  
Kuo-Nan Liou ◽  
Yu Gu ◽  
Jonathan H. Jiang ◽  
Qinbin Li ◽  
...  
Keyword(s):  
Water Vapor ◽  
Radiative Forcing ◽  
Deep Convection ◽  
Significant Negative Correlation ◽  
Formation Mechanisms ◽  
Strong Positive Correlation ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Dry Conditions ◽  
The Impact

Abstract. The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds' net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the Twomey effect for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in-situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.

scholarly journals A case study on the impact of severe convective storms on the water vapor mixing ratio in the lower mid-latitude stratosphere observed in 2019 over Europe

2021 ◽  
Author(s):  
Dina Khordakova ◽  
Christian Rolf ◽  
Jens-Uwe Grooß ◽  
Rolf Müller ◽  
Paul Konopka ◽  
...  
Keyword(s):  
Water Vapor ◽  
North America ◽  
Satellite Data ◽  
Lower Stratosphere ◽  
Radiation Budget ◽  
Climate Feedback ◽  
Sharp Drop ◽  
Vapor Injection ◽  
The Impact

Abstract. Extreme convective events in the troposphere not only have immediate impacts on the surface, they can also influence the dynamics and composition of the lower stratosphere (LS). One major impact is the moistening of the LS by overshooting convection. This effect plays a crucial role in climate feedback as small changes of water vapor in the upper troposphere and lower stratosphere (UTLS) have a large impact on the radiation budget of the atmosphere. In this case study, we investigate water vapor injections into the LS by two consecutive convective events in the European mid-latitudes within the framework of the MOSES (Modular Observation Solutions for Earth Systems) measurement campaign during the early summer of 2019. Using balloon-borne instruments, rare measurements of the convective water vapor injection into the stratosphere were performed. The magnitude of the water vapor reached up to 12.1 ppmv with an estimated background value of 5 ppmv. Hence it is in the same order of magnitude as earlier reports of water vapor injection by convective overshooting above North America. However the overshooting took place in the extra-tropical stratosphere and has an impact on long-term water vapor mixing ratios in the stratosphere compared to the Monsoon-influenced region in North America. At the altitude of the measured injection, a sharp drop in a local ozone enhancement peak makes the observed composition of air very unique with high ozone up to 696 ppbv and high water vapor up to 12.1 ppmv. While ERA-Interim data does not show any signal of the convective overshoot, the measured values in the LS are underestimated by MLS satellite data and overestimated by ERA5 reanalysis data. Backward trajectories of the measured injected air masses reveal that the moistening of the LS took place several hours before the balloon launch. This is in good agreement with reanalyses and satellite data showing a strong change in the structure of isotherms, and a sudden and short-lived increase in potential vorticity at the altitude of the trajectory, as well as low cloud top brightness temperatures during the overshooting event.

A case study on the impact of severe convective storms on the water vapor mixing ratio in the lower mid-latitude stratosphere

2021 ◽  
Author(s):  
Dina Khordakova ◽  
Christian Rolf ◽  
Jens-Uwe Grooß ◽  
Paul Konopka ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Horizontal Resolution ◽  
Early Summer ◽  
Radiation Budget ◽  
Climate Feedback ◽  
Back Trajectories ◽  
Vapor Injection ◽  
The Impact

<p><br>Extreme convective events in the troposphere have not only immediate destructive impact on the surface, but can also influence the dynamic and composition of the lower stratosphere (LS). One of the impacts is the moistening of the LS. This effect plays a crucial role in climate feedback as water vapor in the UTLS (Upper Troposphere/Lower Stratosphere) has a major impact on the radiation budget of the atmosphere. <br>In this case study we investigate water vapor injection into the LS by convective events in mid-latitudes. In the framework of the MOSES (Modular Observation Solutions for Earth Systems) measurement campaign during the early summer of 2019, balloon borne measurements were performed to capture the water vapor injected into the stratosphere by convective events. On two consecutive days the balloon profiles showed clear evidence of water vapor transported above the tropopause by convection. The magnitude of the water vapor enhancement is comparable to other studies which show measurements above North America. At the altitude of the measured injection a sharp cut-off in a local ozone enhancement peak verifies the tropospheric origin of the water vapor injection. Back trajectories of the measured air masses reveal that the moistening took place multiple hours before the balloon launch and correlate well with ERA5 data showing a strong change in the structure of isotherms and a sudden and short lived increase in potential vorticity at the altitude of the trajectory. A comparison with MLS data shows that this process can barely be recognized by satellite measurements due to the low vertical and horizontal resolution. It is hence desirable to increase the number of in-situ measurements focusing on the impacts of convective events on the lower stratosphere over Europe and to assess its impact on UTLS water vapor.</p>

The role of water vapor and cloud feedback on the evolution of the Indian summer monsoon over the last 22,000 years

2020 ◽  
Author(s):  
Chetankumar Jalihal ◽  
Jayaraman Srinivasan ◽  
Arindam Chakraborty
Keyword(s):  
Water Vapor ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Climate Simulation ◽  
Net Energy ◽  
Effect Of Water ◽  
Radiative Feedbacks ◽  
The Impact ◽  
The Last Glacial

<p>In the paleo literature, the emphasis has been on the role of insolation in driving monsoons on orbital timescales, but not on the role of feedbacks internal to the climate system. Here, using the energetics framework, we have underscored the effect of water vapor on the Indian summer monsoon over the last 22,000 years in transient climate simulation, called the TraCE-21K. We show that water vapor amplifies the impact of variations in insolation during cold climates like the Last Glacial Maximum. Insolation affects water vapor through its impact on sea surface temperature. During warmer periods like the Holocene, insolation drives monsoon through its influence on the net energy at the top of the atmosphere. Cloud radiative feedbacks are prominent during these periods. Thus, there are two pathways through which insolation drives monsoons. These pathways can be delineated quantitatively using the energetics. We show further that simultaneous variations in greenhouse gases and ice sheets enhance the effect of water vapor on monsoons. Hence, the sensitivity of monsoon to local summer insolation is different during different periods. Our results suggest that feedbacks play a crucial role in the evolution of Indian monsoon on orbital timescales.</p>

scholarly journals Contributions of Climate Feedbacks to Changes in Atmospheric Circulation

2017 ◽  
Vol 30 (22) ◽  
pp. 9097-9118 ◽  
Author(s):  
Paulo Ceppi ◽  
Theodore G. Shepherd
Keyword(s):  
Water Vapor ◽  
Atmospheric Circulation ◽  
Surface Albedo ◽  
Climate Models ◽  
Cmip5 Models ◽  
Climate Feedbacks ◽  
Wide Range ◽  
Radiative Feedbacks ◽  
Opposing Effects ◽  
The Impact

The projected response of the atmospheric circulation to the radiative changes induced by CO2 forcing and climate feedbacks is currently uncertain. In this modeling study, the impact of CO2-induced climate feedbacks on changes in jet latitude and speed is assessed by imposing surface albedo, cloud, and water vapor feedbacks as if they were forcings in two climate models, CAM4 and ECHAM6. The jet response to radiative feedbacks can be broadly interpreted through changes in midlatitude baroclinicity. Clouds enhance baroclinicity, favoring a strengthened, poleward-shifted jet; this is mitigated by surface albedo changes, which have the opposite effect on baroclinicity and the jet, while water vapor has opposing effects on upper- and lower-level baroclinicity with little net impact on the jet. Large differences between the CAM4 and ECHAM6 responses illustrate how model uncertainty in radiative feedbacks causes a large spread in the baroclinicity response to CO2 forcing. Across the CMIP5 models, differences in shortwave feedbacks by clouds and albedo are a dominant contribution to this spread. Forcing CAM4 with shortwave cloud and albedo feedbacks from a representative set of CMIP5 models yields a wide range of jet responses that strongly correlate with the meridional gradient of the anomalous shortwave heating and the associated baroclinicity response. Differences in shortwave feedbacks statistically explain about 50% of the intermodel spread in CMIP5 jet shifts for the set of models used, demonstrating the importance of constraining radiative feedbacks for accurate projections of circulation changes.

scholarly journals Investigating the impact of cloud-radiative feedbacks on tropical precipitation extremes

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Brian Medeiros ◽  
Amy C. Clement ◽  
James J. Benedict ◽  
Bosong Zhang
Keyword(s):  
Extreme Precipitation ◽  
Climate Models ◽  
Longwave Radiation ◽  
Extreme Rainfall ◽  
Radiative Effects ◽  
Tropical Oceans ◽  
Cloud Radiative Effects ◽  
Radiative Feedbacks ◽  
Mean Climate ◽  
The Impact

AbstractAlthough societally important, extreme precipitation is difficult to represent in climate models. This study shows one robust aspect of extreme precipitation across models: extreme precipitation over tropical oceans is strengthened through a positive feedback with cloud-radiative effects. This connection is shown for a multi-model ensemble with experiments that make clouds transparent to longwave radiation. In all cases, tropical extreme precipitation reduces without cloud-radiative effects. Qualitatively similar results are presented for one model using the cloud-locking method to remove cloud feedbacks. The reduced extreme precipitation without cloud-radiative feedbacks does not arise from changes in the mean climate. Rather, evidence is presented that cloud-radiative feedbacks enhance organization of convection and most extreme precipitation over tropical oceans occurs within organized systems. This result suggests that climate models must correctly predict cloud structure and properties, as well as capture the essence of organized convection in order to accurately represent extreme rainfall.

scholarly journals Impacts of tropical cyclones on the thermodynamic conditions in the tropical tropopause layer observed by A-Train satellites

2021 ◽  
Vol 21 (20) ◽  
pp. 15493-15518
Author(s):  
Jing Feng ◽  
Yi Huang
Keyword(s):  
Water Vapor ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Deep Convection ◽  
Radiative Heating ◽  
Radiative Cooling ◽  
Radiative Balance ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Impact

Abstract. The tropical tropopause layer (TTL) is the transition layer between the troposphere and the stratosphere. Tropical cyclones may impact the TTL by perturbing the vertical distributions of cloud, temperature, and water vapor. This study combines several A-Train instruments, including radar from CloudSat, lidar from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, and the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite, to detect signatures of cyclone impacts on the distribution patterns of cloud, water vapor, temperature, and radiation by compositing these thermodynamic fields relative to the cyclone center location. Based on the CloudSat 2B-CLDCLASS-LIDAR product, this study finds that tropical cyclone events considerably increase the occurrence frequencies of TTL clouds, in the form of cirrus clouds above a clear troposphere. The amount of TTL cloud ice, however, is found to be mostly contributed by overshooting deep convection that penetrates the base of the TTL at 16 km. To overcome the lack of temperature and water vapor products in cloudy conditions, this study implements a synergistic method that retrieves temperature, water vapor, ice water content, and effective radius simultaneously by incorporating observations from AIRS, CloudSat, and CALIPSO. Using the synergistic method, we find a vertically oscillating pattern of temperature anomalies above tropical cyclones, with warming beneath the cloud top (around 16 km) and cooling above. Based on water vapor profiles retrieved by the synergistic method, we find that the layer integrated water vapor (LIWV) above 16 km is higher above tropical cyclones, especially above overshooting deep convective clouds, compared to climatological values. Moreover, we find that the longwave and net radiative cooling effect of clouds prevails within 1000 km of tropical cyclone centers. The radiative heating effects of clouds from the CloudSat 2B-FLXHR-LIDAR product are well differentiated by the collocated brightness temperature of an infrared window channel from the collocated AIRS L1B product. By performing instantaneous radiative heating rate calculations, we further find that TTL hydration is usually associated with radiative cooling of the TTL, which inhibits the diabatic ascent of moist air across isentropic surfaces to the stratosphere. Therefore, the radiative balance of the TTL under the impact of the cyclone does not favor the maintenance of moist anomalies in the TTL or transporting water vertically to the stratosphere.

scholarly journals Impacts of tropical cyclones on the thermodynamic conditions in the tropical tropopause layer observed by A-train satellites

2021 ◽  
Author(s):  
Jing Feng ◽  
Yi Huang
Keyword(s):  
Water Vapor ◽  
Tropical Cyclones ◽  
Distribution Patterns ◽  
Radiative Heating ◽  
Radiative Cooling ◽  
Heating Rates ◽  
Radiative Balance ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Impact

Abstract. The tropical tropopause layer (TTL) is the transition layer between the troposphere and the stratosphere. Tropical cyclones may impact the TTL by perturbing the vertical distributions of cloud, temperature, and water vapor, although this impact is poorly quantified due to the lack of collocated data. To address this problem, we implement a synergistic retrieval approach to obtain the thermodynamic profiles and ice water content above thick high-level clouds using the A-Train satellite measurements that pass over the tropical cyclones. This study detects the signature of cyclone impact on the distribution patterns of cloud, water vapor, temperature, and radiation by compositing these thermodynamic fields with respect to cyclone center locations. It is found that tropical cyclone events considerably increase the occurrence of TTL clouds, in the form of cirrus clouds above a clear troposphere. The amount of TTL cloud ice, however, is found to be mostly contributed by overshooting deep convections that penetrate the bottom of TTL. Using the synergistic retrieval method, we find a vertically oscillating pattern of temperature anomalies above tropical cyclones, with warming beneath the cloud top (around 16 km) and cooling above. The atmospheric column above 16 km is generally hydrated by overshooting convections, although dehydration is detected above non-overshooting TTL clouds. Above overshooting deep convections, the column-integrated water vapor is found to be on average 40 % higher than the climatology. Moreover, the TTL above tropical cyclones is cooled due to longwave radiative cooling. The radiative heating rates above cyclones are well differentiated by the brightness temperature of a satellite infrared channel in the window band. Using radiative calculations, it is found that TTL hydration is usually associated with radiative cooling of the TTL, which inhibits the diabatic ascent of moist air. The radiative balance of the TTL under the impact of the cyclone, therefore, is not in favor of maintaining the moist anomalies in the TTL or transporting water vertically to the stratosphere.

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