An Indirect Effect of Ice Nuclei on Atmospheric Radiation

2009 ◽  
Vol 66 (1) ◽  
pp. 41-61 ◽  
Author(s):  
Xiping Zeng ◽  
Wei-Kuo Tao ◽  
Minghua Zhang ◽  
Arthur Y. Hou ◽  
Shaocheng Xie ◽  
...  
Keyword(s):  
Indirect Effect ◽  
Large Scale ◽  
Three Dimensional ◽  
Radiative Flux ◽  
Middle Latitudes ◽  
Ice Nuclei ◽  
Cloud Resolving Model ◽  
Ice Content ◽  
Cloud Ice ◽  
The Tropics

Abstract A three-dimensional cloud-resolving model (CRM) with observed large-scale forcing is used to study how ice nuclei (IN) affect the net radiative flux at the top of the atmosphere (TOA). In all the numerical experiments carried out, the cloud ice content in the upper troposphere increases with IN number concentration via the Bergeron process. As a result, the upward solar flux at the TOA increases whereas the infrared one decreases. Because of the opposite response of the two fluxes to IN concentration, the sensitivity of the net radiative flux at the TOA to IN concentration varies from one case to another. Six tropical and three midlatitudinal field campaigns provide data to model the effect of IN on radiation in different latitudes. Classifying the CRM simulations into tropical and midlatitudinal and then comparing the two types reveals that the indirect effect of IN on radiation is greater in the middle latitudes than in the tropics. Furthermore, comparisons between model results and observations suggest that observational IN data are necessary to evaluate long-term CRM simulations.

scholarly journals Estimating the Ice Crystal Enhancement Factor in the Tropics

2011 ◽  
Vol 68 (7) ◽  
pp. 1424-1434 ◽  
Author(s):  
Xiping Zeng ◽  
Wei-Kuo Tao ◽  
Toshihisa Matsui ◽  
Shaocheng Xie ◽  
Stephen Lang ◽  
...  
Keyword(s):  
Ice Crystal ◽  
Middle Latitudes ◽  
Ice Nuclei ◽  
Significant Difference ◽  
Physically Based ◽  
Cloud Resolving Model ◽  
The Difference ◽  
The Tropics ◽  
Cloud Condition

Abstract The ice crystal enhancement (IE) factor, defined as the ratio of the ice crystal to ice nuclei (IN) number concentrations for any particular cloud condition, is needed to quantify the contribution of changes in IN to global warming. However, the ensemble characteristics of IE are still unclear. In this paper, a representation of the IE factor is incorporated into a three-ice-category microphysical scheme for use in long-term cloud-resolving model (CRM) simulations. Model results are compared with remote sensing observations, which suggest that, absent a physically based consideration of how IE comes about, the IE factor in tropical clouds is about 103 times larger than that in midlatitudinal ones. This significant difference in IE between the tropics and middle latitudes is consistent with the observation of stronger entrainment and detrainment in the tropics. In addition, the difference also suggests that cloud microphysical parameterizations depend on spatial resolution (or subgrid turbulence parameterizations within CRMs).

scholarly journals Analysis of a rapid increase of stratospheric ozone during late austral summer 2008 over Kerguelen (49.4° S, 70.3° E)

2011 ◽  
Vol 11 (1) ◽  
pp. 363-373 ◽  
Author(s):  
H. Bencherif ◽  
L. El Amraoui ◽  
G. Kirgis ◽  
J. Leclair De Bellevue ◽  
A. Hauchecorne ◽  
...  
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Austral Summer ◽  
Air Masses ◽  
Global Mapping ◽  
The Tropics

Abstract. This paper reports on an increase of ozone event observed over Kerguelen (49.4° S, 70.3° E) in relationship with large-scale isentropic transport. This is evidenced by ground-based observations (co-localised radiosonde and SAOZ experiments) together with satellite global observations (Aura/MLS) assimilated into MOCAGE, a Méteo-France model. The study is based on the analyses of the first ozonesonde experiment never recorded at the Kerguelen site within the framework of a French campaign called ROCK that took place from April to August 2008. Comparisons and interpretations of the observed event are supported by co-localised SAOZ observations, by global mapping of tracers (O3, N2O and columns of O3) from Aura/MLS and Aura/OMI experiments, and by model simulations of Ertel Potential Vorticity initialised by the ECMWF (European Centre for Medium-Range Weather Forecasts) data reanalyses. Satellite and ground-based observational data revealed a consistent increase of ozone in the local stratosphere by mid-April 2008. Additionally, Ozone (O3) and nitrous oxide (N2O) profiles obtained during January–May 2008 using the Microwave Limb Sounder (MLS) aboard the Aura satellite are assimilated into MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle), a global three-dimensional chemistry transport model of Météo-France. The assimilated total O3 values are consistent with SAOZ ground observations (within ±5%), and isentropic distributions of O3 match well with maps of advected potential vorticity (APV) derived from the MIMOSA model, a high-resolution advection transport model, and from the ECMWF reanalysis. The event studied seems to be related to the isentropic transport of air masses that took place simultaneously in the lower- and middle-stratosphere, respectively from the polar region and from the tropics to the mid-latitudes. In fact, the ozone increase observed by mid April 2008 resulted simultaneously: (1) from an equator-ward departure of polar air masses characterised with a high-ozone layer in the lower stratosphere (near the 475 K isentropic level), and (2) from a reverse isentropic transport from the tropics to mid- and high-latitudes in the upper stratosphere (nearby the 700 K level). The increase of ozone observed over Kerguelen from the 16-April ozonesonde profile is thus attributed to a concomitant isentropic transport of ozone in two stratospheric layers: the tropical air moving southward and reaching over Kerguelen in the upper stratosphere, and the polar air passing over the same area but in the lower stratosphere.

scholarly journals Cloud-Resolving Model Simulations of KWAJEX: Model Sensitivities and Comparisons with Satellite and Radar Observations

2007 ◽  
Vol 64 (5) ◽  
pp. 1488-1508 ◽  
Author(s):  
Peter N. Blossey ◽  
Christopher S. Bretherton ◽  
Jasmine Cetrone ◽  
Marat Kharoutdinov
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Longwave Radiation ◽  
Radiative Fluxes ◽  
Model Simulations ◽  
Time Period ◽  
Ground Validation ◽  
Cloud Resolving Model ◽  
Sensitivity Studies ◽  
Upper Level

Abstract Three-dimensional cloud-resolving model simulations of a mesoscale region around Kwajalein Island during the Kwajalein Experiment (KWAJEX) are performed. Using observed winds along with surface and large-scale thermodynamic forcings, the model tracks the observed mean thermodynamic soundings without thermodynamic nudging during 52-day simulations spanning the whole experiment time period, 24 July–14 September 1999. Detailed comparisons of the results with cloud and precipitation observations, including radar reflectivities from the Kwajalein ground validation radar and International Satellite Cloud Climatology Project (ISCCP) cloud amounts and radiative fluxes, reveal the biases and sensitivities of the model’s simulated clouds. The amount and optical depth of high cloud are underpredicted by the model during less rainy periods, leading to excessive outgoing longwave radiation (OLR) and insufficient albedo. The simulated radar reflectivities tend to be excessive, especially in the upper troposphere, suggesting that simulated high clouds are precipitating large hydrometeors too efficiently. Occasionally, large-scale advective forcing errors also seem to contribute to upper-level cloud and relative humidity biases. An extensive suite of sensitivity studies to different microphysical and radiative parameterizations is performed, with surprisingly little impact on the results in most cases.

Retrieval of Latent Heating from TRMM Measurements

2006 ◽  
Vol 87 (11) ◽  
pp. 1555-1572 ◽  
Author(s):  
W.-K. Tao ◽  
E. A. Smith ◽  
R. F. Adler ◽  
Z. S. Haddad ◽  
A. Y. Hou ◽  
...  
Keyword(s):  
Latent Heat ◽  
Large Scale ◽  
Climate Models ◽  
Hydrological Cycle ◽  
Tropical Rainfall Measuring Mission ◽  
Phase Changes ◽  
Latent Heating ◽  
Middle Latitudes ◽  
Rate Profile ◽  
The Tropics

Rainfall is a fundamental process within the Earth's hydrological cycle because it represents a principal forcing term in surface water budgets, while its energetics corollary, latent heating, is the principal source of atmospheric diabatic heating well into the middle latitudes. Latent heat production itself is a consequence of phase changes between the vapor, liquid, and frozen states of water. The properties of the vertical distribution of latent heat release modulate large-scale meridional and zonal circulations within the Tropics, as well as modify the energetic efficiencies of midlatitude weather systems. This paper highlights the retrieval of latent heating from satellite measurements generated by the Tropical Rainfall Measuring Mission (TRMM) satellite observatory, which was launched in November 1997 as a joint American–Japanese space endeavor. Since then, TRMM measurements have been providing credible four-dimensional accounts of rainfall over the global Tropics and subtropics, information that can be used to estimate the space–time structure of latent heating across the Earth's low latitudes. A set of algorithm methodologies for estimating latent heating based on precipitation-rate profile retrievals obtained from TRMM measurements has been under continuous development since the advent of the mission s research program. These algorithms are briefly described, followed by a discussion of the latent heating products that they generate. The paper then provides an overview of how TRMM-derived latent heating information is currently being used in conjunction with global weather and climate models, concluding with remarks intended to stimulate further research on latent heating retrieval from satellites.

Global Gravity Wave Variances from Aura MLS: Characteristics and Interpretation

2008 ◽  
Vol 65 (12) ◽  
pp. 3695-3718 ◽  
Author(s):  
Dong L. Wu ◽  
Stephen D. Eckermann
Keyword(s):  
Gravity Wave ◽  
Global Analysis ◽  
Three Dimensional ◽  
Quasi Biennial Oscillation ◽  
Wind Speeds ◽  
Global Gravity ◽  
Local Background ◽  
Dimensional Weighting ◽  
Cloud Ice ◽  
The Tropics

Abstract The gravity wave (GW)–resolving capabilities of 118-GHz saturated thermal radiances acquired throughout the stratosphere by the Microwave Limb Sounder (MLS) on the Aura satellite are investigated and initial results presented. Because the saturated (optically thick) radiances resolve GW perturbations from a given altitude at different horizontal locations, variances are evaluated at 12 pressure altitudes between ∼21 and 51 km using the 40 saturated radiances found at the bottom of each limb scan. Forward modeling simulations show that these variances are controlled mostly by GWs with vertical wavelengths λz > 5 km and horizontal along-track wavelengths of λy ∼ 100–200 km. The tilted cigar-shaped three-dimensional weighting functions yield highly selective responses to GWs of high intrinsic frequency that propagate toward the instrument. The latter property is used to infer the net meridional component of GW propagation by differencing the variances acquired from ascending (A) and descending (D) orbits. Because of improved vertical resolution and sensitivity, Aura MLS GW variances are ∼5–8 times larger than those from the Upper Atmosphere Research Satellite (UARS) MLS. Like UARS MLS variances, monthly-mean Aura MLS variances in January and July 2005 are enhanced when local background wind speeds are large, due largely to GW visibility effects. Zonal asymmetries in variance maps reveal enhanced GW activity at high latitudes due to forcing by flow over major mountain ranges and at tropical and subtropical latitudes due to enhanced deep convective generation as inferred from contemporaneous MLS cloud-ice data. At 21–28-km altitude (heights not measured by the UARS MLS), GW variance in the tropics is systematically enhanced and shows clear variations with the phase of the quasi-biennial oscillation, in general agreement with GW temperature variances derived from radiosonde, rocketsonde, and limb-scan vertical profiles. GW-induced temperature variances at ∼44-km altitude derived from operational global analysis fields of the ECMWF Integrated Forecast System in August 2006 reveal latitudinal bands of enhanced GW variance and preferred GW meridional propagation directions that are similar to those inferred from the MLS variances, highlighting the potential of MLS GW data for validating the stratospheric GWs simulated and/or parameterized in global models.

scholarly journals Tropospheric column ozone response to ENSO in GEOS-5 assimilation of OMI and MLS ozone data

2016 ◽  
Vol 16 (11) ◽  
pp. 7091-7103 ◽  
Author(s):  
Mark A. Olsen ◽  
Krzysztof Wargan ◽  
Steven Pawson
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Convective Transport ◽  
Vertical Transport ◽  
Small Scale ◽  
Middle Latitudes ◽  
Column Ozone ◽  
The Tropics

Abstract. We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Niño Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Niño 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Niño 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9-year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Niño influence on tropospheric ozone in the middle latitudes.

scholarly journals Transport pathways from the Asian monsoon anticyclone to the stratosphere

2015 ◽  
Vol 15 (18) ◽  
pp. 25981-26023 ◽  
Author(s):  
H. Garny ◽  
W. J. Randel
Keyword(s):  
Large Scale ◽  
Asian Monsoon ◽  
Deep Convection ◽  
Three Dimensional ◽  
Reanalysis Data ◽  
Vertical Transport ◽  
Heating Rates ◽  
Transport Pathways ◽  
Northern Summer ◽  
The Tropics

Abstract. Transport pathways of air originating in the upper tropospheric Asian monsoon anticyclone are investigated based on three-dimensional trajectories. The Asian monsoon anticyclone emerges in response to persistent deep convection over India and southeast Asia in northern summer, and this convection is associated with rapid transport from the surface to the upper troposphere, and possibly into the stratosphere. Here, we investigate the fate of air that originates within the upper tropospheric anticyclone from the outflow of deep convection, using trajectories driven by ERA-interim reanalysis data. Calculations include isentropic estimates, plus fully three-dimensional results based on kinematic and diabatic transport calculations. Isentropic calculations show that air parcels are typically confined within the anticyclone for 10–20 days, and spread over the tropical belt within a month of their initialization. However, only few parcels (3 % at 360 K, 8 % at 380 K) reach the extratropical stratosphere by isentropic mixing. When considering vertical transport we find that 31 % (48%) of the trajectories reach the stratosphere within 60 days when using vertical velocities or diabatic heating rates to calculate vertical transport, respectively. In both cases, most parcels that reach the stratosphere are transported upward within the anticyclone and enter the stratosphere in the tropics, typically 10–20 days after their initialization at 360 K. This suggests that trace gases, including pollutants, that are transported into the stratosphere via the Asian monsoon system are in a position to enter the tropical pipe and thus be transported into the deep stratosphere. Sensitivity calculations with respect to the initial altitude of the trajectories showed that air needs to be transported to levels of 360 K or above by deep convection to likely (≧50 %) reach the stratosphere through transport by the large-scale circulation.

scholarly journals Tropospheric column ozone response to ENSO in GEOS-5 assimilation of OMI and MLS ozone data

2016 ◽  
Author(s):  
M. A. Olsen ◽  
K. Wargan ◽  
S. Pawson
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Convective Transport ◽  
Vertical Transport ◽  
Small Scale ◽  
Middle Latitudes ◽  
Column Ozone ◽  
The Tropics

Abstract. We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Niño Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Niño 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. However, we show a newly identified two-lobed response symmetric about the Equator in the western Pacific/Indonesian region consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Niño 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the nine-year assimilation are representative of the longer-term. This investigation brings insight to several seemingly disparate prior studies of the El Niño influence on tropospheric ozone in the middle latitudes.

scholarly journals Extraction, classification and visualization of 3-dimensional clouds simulated by cloud-resolving atmospheric model

2017 ◽  
Vol 08 (04) ◽  
pp. 1750051 ◽  
Author(s):  
Daisuke Matsuoka
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Vertical Direction ◽  
General Circulation Models ◽  
Atmospheric Model ◽  
Global Scale ◽  
3 Dimensional ◽  
Cloud Ice ◽  
The Tropics ◽  
Atmospheric Phenomena

Cloud-resolving atmospheric general circulation models using large-scale supercomputers reproduce realistic behavior of 3-dimensional atmospheric field on a global scale. To understand the simulation result for scientists, conventional visualization methods based on 2-dimensional cloud classification are not enough for understanding individual clouds and their physical characteristics. In this study, we propose a new 3-dimensional extraction and classification method of simulated clouds based on their 3-dimensional shape and physical properties. Our proposed method extracts individual clouds by cloud water and cloud ice, and classifies them into six types by their altitude and upward flow. We applied the method to time-varying atmospheric simulation data, and attempted to visualize atmospheric phenomena on the tropics such as developing cumulonimbus and tropical cyclone. Two case studies clearly visualize the behavior of individual cloud type and clarify that some cloud types have a relationship with rainfall during active weather phenomena. The proposed method has the potential to analyze such phenomena that develop in the vertical direction as well as the horizontal direction.

scholarly journals Transport pathways from the Asian monsoon anticyclone to the stratosphere

2016 ◽  
Vol 16 (4) ◽  
pp. 2703-2718 ◽  
Author(s):  
Hella Garny ◽  
William J. Randel
Keyword(s):  
Large Scale ◽  
Asian Monsoon ◽  
Deep Convection ◽  
Three Dimensional ◽  
Reanalysis Data ◽  
Vertical Transport ◽  
Heating Rates ◽  
Transport Pathways ◽  
Northern Summer ◽  
The Tropics

Abstract. Transport pathways of air originating in the upper-tropospheric Asian monsoon anticyclone are investigated based on three-dimensional trajectories. The Asian monsoon anticyclone emerges in response to persistent deep convection over India and southeast Asia in northern summer, and this convection is associated with rapid transport from the surface to the upper troposphere and possibly into the stratosphere. Here, we investigate the fate of air that originates within the upper-tropospheric anticyclone from the outflow of deep convection, using trajectories driven by ERA-interim reanalysis data. Calculations include isentropic estimates, plus fully three-dimensional results based on kinematic and diabatic transport calculations. Isentropic calculations show that air parcels are typically confined within the anticyclone for 10–20 days and spread over the tropical belt within a month of their initialization. However, only few parcels (3 % at 360 K, 8 % at 380 K) reach the extratropical stratosphere by isentropic transport. When considering vertical transport we find that 31 %  or 48 % of the trajectories reach the stratosphere within 60 days when using vertical velocities or diabatic heating rates to calculate vertical transport, respectively. In both cases, most parcels that reach the stratosphere are transported upward within the anticyclone and enter the stratosphere in the tropics, typically 10–20 days after their initialization at 360 K. This suggests that trace gases, including pollutants, that are transported into the stratosphere via the Asian monsoon system are in a position to enter the tropical pipe and thus be transported into the deep stratosphere. Sensitivity calculations with respect to the initial altitude of the trajectories showed that air needs to be transported to levels of 360 K or above by deep convection to likely (≧ 50 %) reach the stratosphere through transport by the large-scale circulation.

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