scholarly journals Radiative Cooling, Latent Heating, and Cloud Ice in the Tropical Upper Troposphere

2021 ◽  
pp. 1-39
Keyword(s):  
Heating Rate ◽  
Radiative Cooling ◽  
Convective Heating ◽  
Tropospheric Temperature ◽  
Latent Heating ◽  
Upper Troposphere ◽  
Eddy Heat Flux ◽  
Cloud Ice ◽  
The Impact ◽  
Tropical Upper Troposphere

Abstract The radiative cooling rate in the tropical upper troposphere is expected to increase as climate warms. Since the tropics are approximately in radiative-convective equilibrium (RCE), this implies an increase in the convective heating rate, which is the sum of the latent heating rate and the eddy heat flux convergence. We examine the impact of these changes on the vertical profile of cloud ice amount in cloud-resolving simulations of RCE. Three simulations are conducted: a control run, a warming run, and an experimental run in which there is no warming but a temperature forcing is imposed to mimic the warming-induced increase in radiative cooling. Surface warming causes a reduction in cloud fraction at all upper tropospheric temperature levels but an increase in the ice mixing ratio within deep convective cores. The experimental run has more cloud ice than the warming run at fixed temperature despite the fact that their latent heating rates are equal, which suggests that the efficiency of latent heating by cloud ice increases with warming. An analytic expression relating the ice-related latent heating rate to a number of other factors is derived and used to understand the model results. This reveals that the increase in latent heating efficiency is driven mostly by 1) the migration of isotherms to lower pressure and 2) a slight warming of the top of the convective layer. These physically robust changes act to reduce the residence time of ice along at any particular temperature level, which tempers the response of the mean cloud ice profile to warming.

scholarly journals The impact of lightning on tropospheric ozone chemistry using a new global parametrisation

2016 ◽  
Author(s):  
D. L. Finney ◽  
R. M. Doherty ◽  
O. Wild ◽  
N. L. Abraham
Keyword(s):  
Frequency Distribution ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Upper Troposphere ◽  
Temporal Correlations ◽  
The Uk ◽  
Cloud Ice ◽  
The Impact ◽  
No Emissions ◽  
Tropical Upper Troposphere

Abstract. A lightning parametrisation based on upward cloud ice flux is implemented in a chemistry-climate model (CCM) for the first time. The UK Chemistry and Aerosols model is used to study the impact of these lightning nitric oxide (NO) emissions on ozone. Comparisons are then made between the new ice flux parametrisation and the commonly-used, cloud-top height parametrisation. The ice flux approach improves the simulation of lightning and the temporal correlations with ozone sonde measurements in the middle and upper troposphere. Peak values of ozone in these regions are attributed to high lightning NO emissions. The ice flux approach reduces the overestimation of tropical lightning apparent in this CCM when using the cloud-top approach. This results in less emission in the tropical upper troposphere and more in the extratropics when using the ice flux scheme. In the tropical upper troposphere the reduction in ozone concentration is around 5–10 %. Surprisingly, there is only a small reduction in tropospheric ozone burden when using the ice flux approach. The greatest absolute change in ozone burden is found in the lower stratosphere suggesting that much of the ozone produced in the upper troposphere is transported to higher altitudes. Major differences in the frequency distribution of flash rates for the two approaches are found. The cloud-top height scheme has lower maximum flash rates and more mid-range flash rates than the ice flux scheme. The initial Ox (odd oxygen species) production associated with the frequency distribution of continental lightning is analysed to show that higher flash rates are less efficient at producing Ox – low flash rates produce around 10 times more Ox per flash than high-end flash rates. We find that the newly implemented lightning scheme performs favourably compared to the cloud-top scheme with respect to simulation of lightning and tropospheric ozone. This alternative lightning scheme shows spatial and temporal differences in ozone chemistry which may have implications for comparison on models and observations and for simulation of future changes in tropospheric ozone.

scholarly journals The impact of lightning on tropospheric ozone chemistry using a new global lightning parametrisation

2016 ◽  
Vol 16 (12) ◽  
pp. 7507-7522 ◽  
Author(s):  
D. L. Finney ◽  
R. M. Doherty ◽  
O. Wild ◽  
N. L. Abraham
Keyword(s):  
Frequency Distribution ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Upper Troposphere ◽  
Temporal Correlations ◽  
The Uk ◽  
Cloud Ice ◽  
The Impact ◽  
No Emissions ◽  
Tropical Upper Troposphere

Abstract. A lightning parametrisation based on upward cloud ice flux is implemented in a chemistry–climate model (CCM) for the first time. The UK Chemistry and Aerosols model is used to study the impact of these lightning nitric oxide (NO) emissions on ozone. Comparisons are then made between the new ice flux parametrisation and the commonly used, cloud-top height parametrisation. The ice flux approach improves the simulation of lightning and the temporal correlations with ozone sonde measurements in the middle and upper troposphere. Peak values of ozone in these regions are attributed to high lightning NO emissions. The ice flux approach reduces the overestimation of tropical lightning apparent in this CCM when using the cloud-top approach. This results in less NO emission in the tropical upper troposphere and more in the extratropics when using the ice flux scheme. In the tropical upper troposphere the reduction in ozone concentration is around 5–10 %. Surprisingly, there is only a small reduction in tropospheric ozone burden when using the ice flux approach. The greatest absolute change in ozone burden is found in the lower stratosphere, suggesting that much of the ozone produced in the upper troposphere is transported to higher altitudes. Major differences in the frequency distribution of flash rates for the two approaches are found. The cloud-top height scheme has lower maximum flash rates and more mid-range flash rates than the ice flux scheme. The initial Ox (odd oxygen species) production associated with the frequency distribution of continental lightning is analysed to show that higher flash rates are less efficient at producing Ox; low flash rates initially produce around 10 times more Ox per flash than high-end flash rates. We find that the newly implemented lightning scheme performs favourably compared to the cloud-top scheme with respect to simulation of lightning and tropospheric ozone. This alternative lightning scheme shows spatial and temporal differences in ozone chemistry which may have implications for comparison between models and observations, as well as for simulation of future changes in tropospheric ozone.

The impact of upper tropospheric temperature change on tropical cyclone

2021 ◽  
Author(s):  
Nawo Eguchi ◽  
Kenta Kobayashi ◽  
Kosuke Ito ◽  
Tomoe Nasuno
Keyword(s):  
Tropical Cyclone ◽  
Lower Stratosphere ◽  
Intensity Change ◽  
Tropospheric Temperature ◽  
Upward Motion ◽  
Sea Level Pressure ◽  
Upper Troposphere ◽  
Ocean Coupling ◽  
Cold Simulation ◽  
The Impact

<p>We evaluate the impact of temperature at the upper troposphere and lower stratosphere (UTLS) on the tropical cyclone (TC) generation and its development by using the nonhydrostatic atmosphere-ocean coupling axisymmetric numerical model [Rotunno and Emanuel, 1987; Ito et al., 2010]. In the case of cold simulation at UTLS, the maximum wind and the minimum sea level pressure are increased and decreased than the control run, respectively. The magnitude of intensity change is the approximately 4 times larger than the change estimated from the MPIs (Maximum Potential Intensity [Bister and Emanuel,1998; Holland, 1997]). Further, during the development phase, the cold air mass intrudes to the middle troposphere from the upper troposphere at the center of TC, which is not seen in the warm case, leading the atmosphere unstable and enhanced the upward motion and then the TC got stronger.</p>

scholarly journals Evaluating moist physics for Antarctic mesoscale simulations

1997 ◽  
Vol 25 ◽  
pp. 282-286 ◽  
Author(s):  
Keith M. Hines ◽  
David H. Bromwich ◽  
R. I. Cullather
Keyword(s):  
Mesoscale Model ◽  
Cloud Condensation Nuclei ◽  
Inversion Layer ◽  
Lower Troposphere ◽  
Tropospheric Temperature ◽  
Winter Climate ◽  
Cold Temperatures ◽  
Upper Troposphere ◽  
Downward Longwave Radiation ◽  
Cloud Ice

The performance of an explicit cloud physics parameterization is examined with simulations of high southern latitude winter climate using a version of the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model, version 4. The results reveal that there are three moist physics regimes in the vertical over the elevated interior of Antarctica: the very cold upper troposphere, the relatively warm middle troposphere and the cold boundary layer. Deficiencies for these layers include excessive cloud ice in the upper troposphere, excessive cloud ice in the inversion layer near the ice surface, overly warm temperatures in the lower troposphere, overly cold temperatures in the upper troposphere and excessive downward longwave radiation at the Earth’s surface. Three sensitivity experiments were performed to investigate possible improvements in the cloud parameterization. The results indicate that a reduction of the numerous cloud condensation nuclei, while reducing some errors, appears to be insufficient to improve the simulation. A reduction in the excessive cloud ice in the upper troposphere significantly improves the simulation of upper-tropospheric temperature.

scholarly journals Transport of aerosol pollution in the UTLS during Asian summer monsoon as simulated by ECHAM5-HAMMOZ model

2012 ◽  
Vol 12 (11) ◽  
pp. 30081-30117 ◽  
Author(s):  
S. Fadnavis ◽  
K. Semeniuk ◽  
L. Pozzoli ◽  
M. G. Schultz ◽  
S. D. Ghude ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Indian Subcontinent ◽  
Aerosol Layer ◽  
Anthropogenic Aerosols ◽  
Upper Troposphere ◽  
Aerosol Pollution ◽  
Asian Summer ◽  
Cloud Ice ◽  
The Impact

Abstract. An eight member ensemble of ECHAM5-HAMMOZ simulations for the year 2003 is analyzed to study the transport of aerosols in the Upper Troposphere and Lower Stratosphere (UTLS) during the Asian Summer Monsoon (ASM). Simulations show persistent maxima in black carbon, organic carbon, sulfate, and mineral dust aerosols within the anticyclone in the UTLS throughout the ASM (period from July to September) when convective activity over the Indian subcontinent is highest. Model simulations indicate boundary layer aerosol pollution as the source of this UTLS aerosol layer and identify ASM convection as the dominant transport process. Evidence of ASM transport of aerosols into the stratosphere is observed in HALogen Occultation Experiment (HALOE) and Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction. The impact of aerosols in the UTLS region is analyzed by evaluating the differences between simulations with (CTRL) and without aerosol (HAM-off) loading. The transport of anthropogenic aerosols in the UTLS increases cloud ice, water vapour and temperature, indicating that aerosols play an important role in enhancement of cloud ice in the Upper-Troposphere (UT). Aerosol induced circulation changes include a weakening of the main branch of the Hadley circulation and increased vertical transport around the southern flank of the Himalayas and reduction in monsoon precipitation over the India region.

scholarly journals Large differences in reanalyses of diabatic heating in the tropical upper troposphere and lower stratosphere

2013 ◽  
Vol 13 (18) ◽  
pp. 9565-9576 ◽  
Author(s):  
J. S. Wright ◽  
S. Fueglistaler
Keyword(s):  
Turbulent Mixing ◽  
Lower Stratosphere ◽  
Heat Budget ◽  
Radiative Heating ◽  
Japan Meteorological Agency ◽  
Latent Heating ◽  
Moist Convection ◽  
Climate Data ◽  
Upper Troposphere ◽  
Tropical Upper Troposphere

Abstract. We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), European Reanalysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), Japanese 25-yr Reanalysis and Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS), and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Discrepancies in latent heating reflect continuing difficulties in representing moist convection in models. Although these discrepancies may be expected, their magnitude is still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention). The largest differences in radiative heating in the tropical UTLS are attributable to differences in cloud radiative heating, but important systematic differences are present even in the absence of clouds. Local maxima in heating and cooling due to parameterised turbulent mixing occur in the vicinity of the tropical tropopause.

scholarly journals Evaluating moist physics for Antarctic mesoscale simulations

1997 ◽  
Vol 25 ◽  
pp. 282-286 ◽  
Author(s):  
Keith M. Hines ◽  
David H. Bromwich ◽  
R. I. Cullather
Keyword(s):  
Mesoscale Model ◽  
Cloud Condensation Nuclei ◽  
Inversion Layer ◽  
Lower Troposphere ◽  
Tropospheric Temperature ◽  
Winter Climate ◽  
Cold Temperatures ◽  
Upper Troposphere ◽  
Downward Longwave Radiation ◽  
Cloud Ice

The performance of an explicit cloud physics parameterization is examined with simulations of high southern latitude winter climate using a version of the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model, version 4. The results reveal that there are three moist physics regimes in the vertical over the elevated interior of Antarctica: the very cold upper troposphere, the relatively warm middle troposphere and the cold boundary layer. Deficiencies for these layers include excessive cloud ice in the upper troposphere, excessive cloud ice in the inversion layer near the ice surface, overly warm temperatures in the lower troposphere, overly cold temperatures in the upper troposphere and excessive downward longwave radiation at the Earth’s surface. Three sensitivity experiments were performed to investigate possible improvements in the cloud parameterization. The results indicate that a reduction of the numerous cloud condensation nuclei, while reducing some errors, appears to be insufficient to improve the simulation. A reduction in the excessive cloud ice in the upper troposphere significantly improves the simulation of upper-tropospheric temperature.

scholarly journals Cirrus, Transport, and Mixing in the Tropical Upper Troposphere

2014 ◽  
Vol 71 (4) ◽  
pp. 1339-1352 ◽  
Author(s):  
Tra Dinh ◽  
Stephan Fueglistaler
Keyword(s):  
Radiative Heating ◽  
Transport Time ◽  
Adequate Model ◽  
Upper Troposphere ◽  
Advection Diffusion Equation ◽  
Free Region ◽  
The Mean ◽  
The Individual ◽  
The Impact ◽  
Tropical Upper Troposphere

Abstract The impact of cloud radiative heating on transport time scales from the tropical upper troposphere to the stratosphere is studied in two-dimensional numerical simulations. Clouds are idealized as sources of radiative heating and are stochastically distributed in space and time. A spatial probability function constrains clouds to occur in only part of the domain to depict heterogeneously distributed clouds in the atmosphere. The transport time from the lower to upper boundaries (age of air) is evaluated with trajectories. The spectra of age of air obtained in the simulations are bimodal, with the first mode composed of trajectories that remain in the cloudy part of the domain during their passages from the lower to upper boundaries, and the second mode composed of the remaining trajectories that visit the cloud-free regions. For the first group of trajectories only, the mean age scales inversely with the time-mean radiative heating in cloudy air, and the one-dimensional advection–diffusion equation provides an adequate model for transport. However, the exchange between the cloudy and cloud-free regions renders the mean age over all trajectories (including those that visit the cloud-free region) much longer than the time expected if all air parcels remain in cloudy air. In addition, the overall mean age is not inversely proportional to the time-mean heating rate in cloudy air. Sensitivity calculations further show that the sizes, durations, and amplitudes of the individual clouds are also important to the transport time. The results show that the frequently used decomposition of radiative heating into clear-sky and cloud radiative heating may give incorrect interpretations regarding the time scale of transport into the stratosphere.

scholarly journals Jupiter's post-impact atmospheric thermal response

1996 ◽  
Vol 156 ◽  
pp. 293-306
Author(s):  
Barney J. Conrath
Keyword(s):  
Time Scales ◽  
Thermal Emission ◽  
Thermal Structure ◽  
Radiative Cooling ◽  
Temperature Perturbation ◽  
Ambient Atmosphere ◽  
Height Range ◽  
Upper Troposphere ◽  
Entire Height ◽  
The Impact

Measurements of thermal emission in spectral regions, ranging from the near-infrared to mm wavelengths provide information on the atmospheric thermal structure over impact sites fromμbar levels in the upper stratosphere down to the upper troposphere. Systematic time series of observations relevant to this entire height range over individual spots do not exist. However, by piecing together information at different times from various spots, it is possible to obtain a provisional, semi-quantitative picture of the behavior of the thermal structure over a typical impact site. Immediately after fall-back of the ejecta plume, the upper stratosphere is heated to ∼ 600-1300 K above ambient temperature. The amplitude of the temperature perturbation diminishes with increasing depth in the atmosphere, but even in the upper troposphere a temperature increase of a few kelvins is observed. Initially, the upper stratosphere cools very rapidly with time scales of tens of minutes, presumably the result of strong radiative cooling associated with the high temperatures. After the initial cooling, all levels continue to cool at slower rates with time scales of a few days; however, this is still very rapid compared to radiative cooling of the ambient atmosphere. Enhancements in infrared opacity necessary to produce the cooling radiatively do not appear to be viable, suggesting that dynamical effects may play a dominant role. Possible mechanisms include horizontal mixing with the ambient atmosphere and adiabatic cooling produced by upward motion associated with an anticyclonic vortex. Many questions remain concerning the thermal structure above the impact sites; these are being addressed through ongoing data analysis and modeling efforts.

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