Relationship between surface and tropospheric water vapor variation on interannual timescale: A revisit

2020 ◽  
Author(s):  
Mengmiao Yang ◽  
De-Zheng Sun ◽  
Guang J. Zhang
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Deep Convection ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
Moisture Regime ◽  
Strongly Correlated ◽  
Strongly Coupled ◽  
Significant Difference ◽  
The Tropics

<p><span>It is an old question whether tropospheric water vapor at different levels changes consistently in response to the enhanced greenhouse gas in the atmosphere. Earlier studies using older versions of climate models and available data revealed a significant difference between models and observations. Water vapor changes in the interior of the tropical troposphere have been found to be more strongly coupled to changes at the surface in climate models than in observations. We reexamine this issue using four leading CMIP5 models (CCSM4, HadGEM2-A, GFDL-CM3 and MPI-ESM-MR) and more updated observational datasets (ERA-Interim and NCEP reanalysis). Focusing on the Tropics, we have calculated the correlations between interannual variation of specific humidity in all levels of the troposphere with that at the surface. It is found that the previously noted biases in the strength of the coupling between water vapor changes in the interior of the troposphere and those at the surface still exist in the updated models—the change in the tropical averaged tropospheric water vapor is more strongly correlated with the change in the surface, especially in the middle troposphere. It is argued that the vertical profile of water vapor correlations in observations is more consistent with the “hot tower” concept for tropical convections. Zonal mean correlation results and those from the moisture regime sorting method are consistent with each other, both of which indicate the role of deep convection as a mechanism to couple the middle tropospheric water vapor and that in the surface and that an inaccurate representation of deep convection as a possible cause for the discrepancies between models and observations in the coupling between middle tropospheric water vapor and those at the surface.</span></p>

scholarly journals Estimates of the Water Vapor Climate Feedback during El Niño–Southern Oscillation

2009 ◽  
Vol 22 (23) ◽  
pp. 6404-6412 ◽  
Author(s):  
A. E. Dessler ◽  
S. Wong
Keyword(s):  
Global Warming ◽  
Water Vapor ◽  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Specific Humidity ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Water Vapor Feedback

Abstract The strength of the water vapor feedback has been estimated by analyzing the changes in tropospheric specific humidity during El Niño–Southern Oscillation (ENSO) cycles. This analysis is done in climate models driven by observed sea surface temperatures [Atmospheric Model Intercomparison Project (AMIP) runs], preindustrial runs of fully coupled climate models, and in two reanalysis products, the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) and the NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA). The water vapor feedback during ENSO-driven climate variations in the AMIP models ranges from 1.9 to 3.7 W m−2 K−1, in the control runs it ranges from 1.4 to 3.9 W m−2 K−1, and in the ERA-40 and MERRA it is 3.7 and 4.7 W m−2 K−1, respectively. Taken as a group, these values are higher than previous estimates of the water vapor feedback in response to century-long global warming. Also examined is the reason for the large spread in the ENSO-driven water vapor feedback among the models and between the models and the reanalyses. The models and the reanalyses show a consistent relationship between the variations in the tropical surface temperature over an ENSO cycle and the radiative response to the associated changes in specific humidity. However, the feedback is defined as the ratio of the radiative response to the change in the global average temperature. Differences in extratropical temperatures will, therefore, lead to different inferred feedbacks, and this is the root cause of spread in feedbacks observed here. This is also the likely reason that the feedback inferred from ENSO is larger than for long-term global warming.

scholarly journals A statistical analysis of the influence of deep convection on water vapor variability in the tropical upper troposphere

2009 ◽  
Vol 9 (15) ◽  
pp. 5847-5864 ◽  
Author(s):  
J. S. Wright ◽  
R. Fu ◽  
A. J. Heymsfield
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Upper Troposphere ◽  
Ambient Relative Humidity ◽  
Wide Range ◽  
Ice Water Content ◽  
The Tropics ◽  
Ice Water ◽  
Tropical Upper Troposphere

Abstract. The factors that control the influence of deep convective detrainment on water vapor in the tropical upper troposphere are examined using observations from multiple satellites in conjunction with a trajectory model. Deep convection is confirmed to act primarily as a moisture source to the upper troposphere, modulated by the ambient relative humidity (RH). Convective detrainment provides strong moistening at low RH and offsets drying due to subsidence across a wide range of RH. Strong day-to-day moistening and drying takes place most frequently in relatively dry transition zones, where between 0.01% and 0.1% of Tropical Rainfall Measuring Mission Precipitation Radar observations indicate active convection. Many of these strong moistening events in the tropics can be directly attributed to detrainment from recent tropical convection, while others in the subtropics appear to be related to stratosphere-troposphere exchange. The temporal and spatial limits of the convective source are estimated to be about 36–48 h and 600–1500 km, respectively, consistent with the lifetimes of detrainment cirrus clouds. Larger amounts of detrained ice are associated with enhanced upper tropospheric moistening in both absolute and relative terms. In particular, an increase in ice water content of approximately 400% corresponds to a 10–90% increase in the likelihood of moistening and a 30–50% increase in the magnitude of moistening.

scholarly journals Tropical convection regimes in climate models: evaluation with satellite observations

2017 ◽  
Author(s):  
Andrea K. Steiner ◽  
Bettina C. Lackner ◽  
Mark A. Ringer
Keyword(s):  
Climate Models ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Atmospheric Temperature ◽  
Tropical Convection ◽  
Specific Humidity ◽  
Moist Convection ◽  
Tropopause Region ◽  
Tropical Troposphere ◽  
Unique Source

Abstract. High quality observations are powerful tools for the evaluation of climate models towards improvement and reduction of uncertainty. Particularly at low latitudes, the most uncertain aspect lies in the representation of moist convection and interaction with dynamics, where rising motion is tied to deep convection and sinking motion to dry regimes. Since humidity is closely coupled with temperature feedbacks in the tropical troposphere a proper representation of this region is essential. Here we demonstrate the evaluation of atmospheric climate models with satellite-based observations from Global Positioning System (GPS) radio occultation (RO), which feature high vertical resolution and accuracy in the troposphere to lower stratosphere. We focus on the representation of the vertical atmospheric structure in tropical convection regimes, defined by high updraft velocity over warm surfaces, and investigate atmospheric temperature and humidity profiles. Results reveal that some models do not fully capture convection regions, particularly over land, and only partly represent high updraft or downdraft velocities. Models show large biases in tropical mean temperature of more than 4 K in the tropopause region and the lower stratosphere. Reasonable agreement with observations is given in mean specific humidity in the lower to mid-troposphere. In moist convection regions, models tend to underestimate moisture by 10 % to 30 % over oceans whereas in dry downdraft regions they overestimate moisture by 100 %. Our findings provide evidence that RO observations are a unique source of information, with a range of further atmospheric variables to be exploited, for the evaluation and advancement of next generation climate models.

scholarly journals Processes Controlling Tropical Tropopause Temperature and Stratospheric Water Vapor in Climate Models

2015 ◽  
Vol 28 (16) ◽  
pp. 6516-6535 ◽  
Author(s):  
Steven C. Hardiman ◽  
Ian A. Boutle ◽  
Andrew C. Bushell ◽  
Neal Butchart ◽  
Mike J. P. Cullen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Atmospheric Composition ◽  
Stratospheric Water Vapor ◽  
Vertical Advection ◽  
Radiative Processes ◽  
Microphysical Properties ◽  
Tropical Tropopause ◽  
The Tropics ◽  
Tropopause Temperature

Abstract A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.

Thermodynamic Scaling of the Hydrological Cycle of the Last Glacial Maximum

2012 ◽  
Vol 25 (3) ◽  
pp. 992-1006 ◽  
Author(s):  
William R. Boos
Keyword(s):  
Water Vapor ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Hydrological Cycle ◽  
High Latitudes ◽  
Last Glacial ◽  
The Tropics ◽  
The Last Glacial Maximum ◽  
Circulation Changes ◽  
The Last Glacial

Abstract In climate models subject to greenhouse gas–induced warming, vertically integrated water vapor increases at nearly the same rate as its saturation value. Previous studies showed that this increase dominates circulation changes in climate models, so that precipitation minus evaporation (P − E) decreases in the subtropics and increases in the tropics and high latitudes at a rate consistent with a Clausius–Clapeyron scaling. This study examines whether the same thermodynamic scaling describes differences in the hydrological cycle between modern times and the last glacial maximum (LGM), as simulated by a suite of coupled ocean–atmosphere models. In these models, changes in water vapor between modern and LGM climates do scale with temperature according to Clausius–Clapeyron, but this thermodynamic scaling provides a poorer description of the changes in P − E. While the scaling is qualitatively consistent with simulations in the zonal mean, predicting higher P − E in the subtropics and lower P − E in the tropics and high latitudes, it fails to account for high-amplitude zonal asymmetries. Large horizontal gradients of temperature change, which are often neglected when applying the scaling to next-century warming, are shown to be important in large parts of the extratropics. However, even with this correction the thermodynamic scaling provides a poor quantitative fit to the simulations. This suggests that circulation changes play a dominant role in regional hydrological change between modern and LGM climates. Changes in transient eddy moisture transports are shown to be particularly important, even in the deep tropics. Implications for the selection and interpretation of climate proxies are discussed.

scholarly journals Mechanisms of Future Predicted Changes in the Zonal Mean Mid-Latitude Circulation

2019 ◽  
Vol 5 (4) ◽  
pp. 345-357 ◽  
Author(s):  
Tiffany A. Shaw
Keyword(s):  
Heat Release ◽  
Latent Heat ◽  
Climate Models ◽  
Static Stability ◽  
Hadley Cell ◽  
Specific Humidity ◽  
Latent Heat Release ◽  
Starting Point ◽  
Intensity Changes ◽  
The Tropics

AbstractState-of-the-art climate models predict the zonal mean mid-latitude circulation will undergo a poleward shift and seasonally and hemispherically dependent intensity changes in the future. Here I review the mechanisms put forward to explain the zonal mean mid-latitude circulation response to increased carbon dioxide (CO2) concentration. The mechanisms are grouped according to their thermodynamic starting point, which are thought to arise from processes independent of the zonal mean mid-latitude circulation response. There are 24 mechanisms and 8 thermodynamic starting points: (i) increased latent heat release aloft in the tropics, (ii) increased dry static stability and tropopause height outside the tropics, (iii) radiative cooling of the stratosphere, (iv) Hadley cell expansion, (v) increased specific humidity following the Clausius-Clapeyron relation, (vi) cloud radiative effect changes, (vii) turbulent surface heat flux changes, and (viii) decreased surface meridional temperature gradient. I argue progress can be made by testing the thermodynamic starting points. I review recent tests of the increased latent heat release aloft in the tropics starting point, i.e., prescribing diabatic perturbations, quantifying the transient response to an abrupt CO2 increase and imposing latitudinally dependent CO2 concentration. Finally, I provide a future outlook for improving our understanding of predicted changes in the zonal mean mid-latitude circulation.

Understanding the role of water vapor and temperature in easterly wave-related convection

2020 ◽  
Author(s):  
Rosa Vargas Martes ◽  
Angel Adames Corraliza
Keyword(s):  
Water Vapor ◽  
Rainfall Variability ◽  
Large Fraction ◽  
Deep Convection ◽  
Linear Regression Analysis ◽  
Empirical Orthogonal Functions ◽  
Specific Humidity ◽  
Coupling Mechanism ◽  
Orthogonal Functions ◽  
The Relationship

<p>Easterly Waves (EW) in the Pacific Ocean (PEW) and over Africa (AEW) account for a large fraction of rainfall variability in their respective regions. Although multiple studies have been conducted to better understand EWs, many questions remain regarding their structure, development, and coupling to deep convection. Recent studies have highlighted the relationship between water vapor and precipitation in tropical motion systems. However, EW have not been studied within this context. On the basis of Empirical Orthogonal Functions (EOFs) and a novel plume-buoyancy framework, the thermodynamic processes associated with EW-related convection are elucidated. A linear regression analysis reveals the relationship between temperature, moisture, and precipitation in EW. Temperature anomalies are found to be highly correlated in space and time with anomalies in specific humidity. However, this coupling between temperature and moisture is more robust in AEWs than PEWs. In PEWs moisture accounts for a larger fraction of precipitation variability. Results suggest that the convective coupling mechanism in AEW may differ from the coupling mechanism of PEWs.</p>

Regionally Varying Assessments of Upper-Level Tropical Width in Reanalyses and CMIP5 Models Using a Tropopause Break Metric

2020 ◽  
Vol 33 (14) ◽  
pp. 5885-5903 ◽  
Author(s):  
Elinor R. Martin ◽  
Cameron R. Homeyer ◽  
Roarke A. McKinzie ◽  
Kevin M. McCarthy ◽  
Tao Xian
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Models ◽  
Cmip5 Models ◽  
The Past ◽  
East Pacific ◽  
Change Climate ◽  
Upper Level ◽  
The Tropics

AbstractChanges in tropical width can have important consequences in sectors including ecosystems, agriculture, and health. Observations suggest tropical expansion over the past 30 years although studies have not agreed on the magnitude of this change. Climate model projections have also indicated an expansion and show similar uncertainty in its magnitude. This study utilizes an objective, longitudinally varying, tropopause break method to define the extent of the tropics at upper levels. The location of the tropopause break is associated with enhanced stratosphere–troposphere exchange and thus its structure influences the chemical composition of the stratosphere. The method shows regional variations in the width of the upper-level tropics in the past and future. Four modern reanalyses show significant contraction of the tropics over the eastern Pacific between 1981 and 2015, and slight but significant expansion in other regions. The east Pacific narrowing contributes to zonal mean narrowing, contradicting prior work, and is attributed to the use of monthly and zonal mean data in prior studies. Six global climate models perform well in representing the climatological location of the tropical boundary. Future projections show a spread in the width trend (from ~0.5° decade−1 of narrowing to ~0.4° decade−1 of widening), with a narrowing projected across the east Pacific and Northern Hemisphere Americas. This study illustrates that this objective tropopause break method that uses instantaneous data and does not require zonal averaging is appropriate for identifying upper-level tropical width trends and the break location is connected with local and regional changes in precipitation.

Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation

2017 ◽  
Vol 74 (3) ◽  
pp. 915-931 ◽  
Author(s):  
Yi-Hung Kuo ◽  
J. David Neelin ◽  
C. Roberto Mechoso
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
High Time Resolution ◽  
Fast Time ◽  
Additional Line ◽  
Turbulent Entrainment ◽  
Community Earth System Model ◽  
Atmospheric Radiation Measurement ◽  
Simulated Climate ◽  
The Tropics

Abstract Previous work by various authors has pointed to the role of lower-free-tropospheric humidity in affecting the onset of deep convection in the tropics. Empirical relationships between column water vapor (CWV) and precipitation have been inferred to result from these effects. Evidence from previous work has included deep convective conditional instability calculations for entraining plumes, in which the lower-free-tropospheric environment affects the onset of deep convection due to the differential impact on buoyancy of turbulent entrainment of dry versus moist air. The relationship between deep convection and water vapor is, however, a two-way interaction because convection also moistens the free troposphere. The present study adds an additional line of evidence toward fully establishing the causality of the precipitation–water vapor relationship. Parameter perturbation experiments using the coupled Community Earth System Model (CESM) with high-time-resolution output are analyzed for a set of statistics for the transition to deep convection, coordinated with observational diagnostics for the Green Ocean Amazon (GOAmazon) campaign and tropical western Pacific Atmospheric Radiation Measurement (ARM) sites. For low values of entrainment in the deep convective scheme, these statistics are radically altered and the observed pickup of precipitation with CWV is no longer seen. In addition to helping cement the dominant direction of causality in the fast-time-scale precipitation–CWV relationship, the results point to impacts of entrainment on the climatology. Because at low entrainment convection can fire before tropospheric moistening, the climatological values of relative humidity are lower than observed. These findings can be consequential to biases in simulated climate and to projections of climate change.

scholarly journals An Evaluation of Northern Australian Wet Season Rainfall Bursts in CMIP5 Models

2018 ◽  
Vol 31 (19) ◽  
pp. 7789-7802 ◽  
Author(s):  
Sugata Narsey ◽  
Michael J. Reeder ◽  
Christian Jakob ◽  
Duncan Ackerley
Keyword(s):  
Outgoing Longwave Radiation ◽  
Climate Models ◽  
Longwave Radiation ◽  
Cmip5 Models ◽  
Madden Julian Oscillation ◽  
Wet Season ◽  
The North ◽  
Coupled Climate Models ◽  
The Tropics ◽  
The Relationship

The simulation of northern Australian wet season rainfall bursts by coupled climate models is evaluated. Individual models produce vastly different amounts of precipitation over the north of Australia during the wet season, and this is found to be related to the number of bursts they produce. The seasonal cycle of bursts is found to be poor in most of the models evaluated. It is known that northern Australian wet season bursts are often associated with midlatitude Rossby wave packets and their surface signature as they are refracted toward the tropics. The relationship between midlatitude waves and the initiation of wet season bursts is simulated well by the models evaluated. Another well-documented influence on the initiation of northern Australian wet season bursts is the Madden–Julian oscillation (MJO). No model adequately simulated the tropical outgoing longwave radiation temporal–spatial patterns seen in the reanalysis-derived OLR. This result suggests that the connection between the MJO and the initiation of northern Australian wet season bursts in models is poor.

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