comment on “Impact of poleward heat and moisture transports on Arctic clouds and climate simulation”

Abstract. Many general circulation models (GCMs) have difficulty simulating Arctic clouds and climate, causing substantial inter-model spread. To address this issue, two Atmospheric Model Intercomparison Project (AMIP) simulations from the Community Atmosphere Model version 5 (CAM5) and Seoul National University (SNU) Atmosphere Model version 0 (SAM0) with a unified convection scheme (UNICON) are employed to identify an effective mechanism for improving Arctic cloud and climate simulations. Over the Arctic, SAM0 produced a larger cloud fraction and cloud liquid mass than CAM5, reducing the negative Arctic cloud biases in CAM5. The analysis of cloud water condensation rates indicates that this improvement is associated with an enhanced net condensation rate of water vapor into the liquid condensate of Arctic low-level clouds, which in turn is driven by enhanced poleward transports of heat and moisture by the mean meridional circulation and transient eddies. The reduced Arctic cloud biases lead to improved simulations of surface radiation fluxes and near-surface air temperature over the Arctic throughout the year. The association between the enhanced poleward transports of heat and moisture and increase in liquid clouds over the Arctic is also evident not only in both models, but also in the multi-model analysis. Our study demonstrates that enhanced poleward heat and moisture transport in a model can improve simulations of Arctic clouds and climate.

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Decadal changes of wintertime poleward heat and moisture transport associated with the amplified Arctic warming

10.21203/rs.3.rs-264481/v1 ◽

2021 ◽

Author(s):

Xiaozhuo Sang ◽

Xiu-Qun Yang ◽

Lingfeng Tao ◽

Jiabei Fang ◽

Xuguang Sun

Keyword(s):

Heat Transport ◽

Moisture Transport ◽

Stationary Wave ◽

The Arctic ◽

Stationary Waves ◽

High Latitudes ◽

Arctic Warming ◽

Poleward Heat Transport ◽

Heat And Moisture ◽

Moisture Transports

Abstract The Arctic warming, especially during winter, has been almost twice as large as the global average since the late 1990s, which is known as the Arctic amplification. Yet linkage between the amplified Arctic warming and the midlatitude change is still under debate. This study examines the decadal changes of wintertime poleward heat and moisture transports between two 18-yr epochs (1999–2016 and 1981–1998) with five atmospheric reanalyses. It is found that the wintertime Arctic warming induces an amplification of the high latitude stationary wave component of zonal wavenumber one but a weakening of the wavenumber two. These stationary wave changes enhance poleward heat and moisture transports, which are conducive to further Arctic warming and moistening, acting as a positive feedback onto the Arctic warming. Meanwhile, the Arctic warming reduces atmospheric baroclinicity and thus weakens synoptic eddy activities in the high latitudes. The decreased transient eddy activities reduce poleward heat and moisture transports, which decrease the Arctic temperature and moisture, acting as a negative feedback onto the Arctic warming. The total poleward heat transport contributes little to the Arctic warming, since the increased poleward heat transport by stationary waves is nearly canceled by the decreased transport by transient eddies. However, the total poleward moisture transport increases over most areas of the high latitudes that is dominated by the increased transport by stationary waves, which provides a significant net positive feedback onto the Arctic warming and moistening. Such a poleward moisture transport feedback may be particularly crucial to the amplified Arctic warming during winter when the ice-albedo feedback vanishes.

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Amazon Coastal Squall Lines. Part II: Heat and Moisture Transports

Monthly Weather Review ◽

10.1175/1520-0493(1994)122<0623:acslpi>2.0.co;2 ◽

1994 ◽

Vol 122 (4) ◽

pp. 623-635 ◽

Cited By ~ 26

Author(s):

Steven Greco ◽

John Scala ◽

Jeffrey Halverson ◽

Harold L. Massie ◽

Wei-Kuo Tao ◽

...

Keyword(s):

Squall Lines ◽

Heat And Moisture ◽

Moisture Transports

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Global Thermohaline Circulation. Part II: Sensitivity with Interactive Atmospheric Transports

Journal of Climate ◽

10.1175/1520-0442-12.1.83 ◽

1999 ◽

Vol 12 (1) ◽

pp. 83-91 ◽

Cited By ~ 14

Author(s):

Xiaoli Wang ◽

Peter H. Stone ◽

Jochem Marotzke

Keyword(s):

Southern Hemisphere ◽

General Circulation ◽

Large Scale ◽

Thermohaline Circulation ◽

Circulation Model ◽

Ocean Atmosphere ◽

Heat And Moisture ◽

Sst Gradient ◽

Moisture Transports ◽

Flux Adjustment

Abstract A hybrid coupled ocean–atmosphere model is used to investigate the stability of the thermohaline circulation (THC) to an increase in the surface freshwater forcing in the presence of interactive meridional transports in the atmosphere. The ocean component is the idealized global general circulation model used in Part I. The atmospheric model assumes fixed latitudinal structure of the heat and moisture transports, and the amplitudes are calculated separately for each hemisphere from the large-scale sea surface temperature (SST) and SST gradient, using parameterizations based on baroclinic stability theory. The ocean–atmosphere heat and freshwater exchanges are calculated as residuals of the steady-state atmospheric budgets. Owing to the ocean component’s weak heat transport, the model has too strong a meridional SST gradient when driven with observed atmospheric meridional transports. When the latter are made interactive, the conveyor belt circulation collapses. A flux adjustment is introduced in which the efficiency of the atmospheric transports is lowered to match the too low efficiency of the ocean component. The feedbacks between the THC and both the atmospheric heat and moisture transports are positive, whether atmospheric transports are interactive in the Northern Hemisphere, the Southern Hemisphere, or both. However, the feedbacks operate differently in the Northern and Southern Hemispheres, because the Pacific THC dominates in the Southern Hemisphere, and deep water formation in the two hemispheres is negatively correlated. The feedbacks in the two hemispheres do not necessarily reinforce each other because they have opposite effects on low-latitude temperatures. The model is qualitatively similar in stability to one with conventional “additive” flux adjustment, but quantitatively more stable.

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Impact of poleward heat and moisture transports on Arctic clouds and climate simulation

10.5194/acp-2019-199 ◽

2019 ◽

Author(s):

Eun-Hyuk Baek ◽

Joo-Hong Kim ◽

Sungsu Park ◽

Baek-Min Kim ◽

Jee-Hoon Jeong

Keyword(s):

Global Radiation ◽

Surface Radiation ◽

Radiation Budget ◽

The Arctic ◽

Near Surface ◽

Arctic Clouds ◽

Model Version ◽

Budget Analysis ◽

Atmosphere Model ◽

Heat And Moisture

Abstract. Clouds play an important role in regulating the Earth's global radiation budget. Many General Circulation Models (GCMs) have difficulty in simulating Arctic clouds and climate with a large inter-model spread. In an attempt to address this issue, we compare an Atmospheric Model Inter-comparison Project (AMIP) simulation from the Community Atmosphere Model version 5 (CAM5) with that from the Seoul National University (SNU) Atmosphere Model version 0 with a Unified Convection Scheme (SAM0). Over the Arctic, it was found that SAM0 simulates more cloud fraction and cloud liquid mass than CAM5, reducing the Arctic clouds biases in CAM5. The budget analysis indicates that this improvement is associated with an enhanced net condensation rate of water vapor into the liquid condensate of the Arctic low-level stratus, which in turn is driven by enhanced poleward transports of heat and moisture by mean meridional circulation and transient eddies. The reduced Arctic cloud biases lead to improved simulations of surface radiation fluxes and near-surface air temperature over the Arctic throughout the year. The association between the enhanced poleward transports of heat and moisture and more liquid stratus over the Arctic is also evident in the multi-models analysis. Our study indicates that the proper simulation of poleward heat and moisture transport is one of the key factors necessary for improving the simulations of Arctic clouds and climate.

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Eddy Momentum, Heat, and Moisture Transports During the Boreal Winter: Three Reanalysis Data Comparison

Atmosphere ◽

10.14191/atmos.2016.26.4.649 ◽

2016 ◽

Vol 26 (4) ◽

pp. 649-663

Author(s):

Hyejin Moon ◽

Kyung-Ja Ha

Keyword(s):

Reanalysis Data ◽

Boreal Winter ◽

Data Comparison ◽

Heat And Moisture ◽

Moisture Transports

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The Shikani HME: A New Tracheostomy Heat and Moisture Exchanger

Journal of Speech Language and Hearing Research ◽

10.1044/2020_jslhr-19-00107 ◽

2020 ◽

Vol 63 (9) ◽

pp. 2921-2929

Author(s):

Alan H. Shikani ◽

Elamin M. Elamin ◽

Andrew C. Miller

Keyword(s):

Ex Vivo ◽

Moisture Loss ◽

Speaking Valve ◽

Time Zero ◽

In Series ◽

Turbulent Airflow ◽

The Difference ◽

Loss Efficiency ◽

Heat And Moisture ◽

Lung Simulation

Purpose Tracheostomy patients face many adversities including loss of phonation and essential airway functions including air filtering, warming, and humidification. Heat and moisture exchangers (HMEs) facilitate humidification and filtering of inspired air. The Shikani HME (S-HME) is a novel turbulent airflow HME that may be used in-line with the Shikani Speaking Valve (SSV), allowing for uniquely preserved phonation during humidification. The aims of this study were to (a) compare the airflow resistance ( R airflow ) and humidification efficiency of the S-HME and the Mallinckrodt Tracheolife II tracheostomy HME (M-HME) when dry (time zero) and wet (after 24 hr) and (b) determine if in-line application of the S-HME with a tracheostomy speaking valve significantly increases R airflow over a tracheostomy speaking valve alone (whether SSV or Passy Muir Valve [PMV]). Method A prospective observational ex vivo study was conducted using a pneumotachometer lung simulation unit to measure airflow ( Q ) amplitude and R airflow , as indicated by a pressure drop ( P Drop ) across the device (S-HME, M-HME, SSV + S-HME, and PMV). Additionally, P Drop was studied for the S-HME and M-HME when dry at time zero (T 0 ) and after 24 hr of moisture testing (T 24 ) at Q of 0.5, 1, and 1.5 L/s. Results R airflow was significantly less for the S-HME than M-HME (T 0 and T 24 ). R airflow of the SSV + S-HME in series did not significant increase R airflow over the SSV or PMV alone. Moisture loss efficiency trended toward greater efficiency for the S-HME; however, the difference was not statistically significant. Conclusions The turbulent flow S-HME provides heat and moisture exchange with similar or greater efficacy than the widely used laminar airflow M-HME, but with significantly lower resistance. The S-HME also allows the innovative advantage of in-line use with the SSV, hence allowing concurrent humidification and phonation during application, without having to manipulate either device.

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