The Observed Water Vapor Budget in an Atmospheric River over the Northeast Pacific

AbstractCombined airborne, shipboard, and satellite measurements provide the first observational assessment of all major terms of the vertically integrated water vapor (IWV) budget for a 150 km × 160 km region within the core of a strong atmospheric river over the northeastern Pacific Ocean centered on 1930 UTC 5 February 2015. Column-integrated moisture flux convergence is estimated from eight dropsonde profiles, and surface rain rate is estimated from tail Doppler radar reflectivity measurements. Dynamical convergence of water vapor (2.20 ± 0.12 mm h−1) nearly balances estimated precipitation (2.47 ± 0.41 mm h−1), but surface evaporation (0.0 ± 0.05 mm h−1) is negligible. Advection of drier air into the budget region (−1.50 ± 0.21 mm h−1) causes IWV tendency from the sum of all terms to be negative (−1.66 ± 0.45 mm h−1). An independent estimate of IWV tendency obtained from the difference between IWV measured by dropsonde and retrieved by satellite 3 h earlier is less negative (−0.52 ± 0.24 mm h−1), suggesting the presence of substantial temporal variability that is smoothed out when averaging over several hours. The calculation of budget terms for various combinations of dropsonde subsets indicates the presence of substantial spatial variability at ~50-km scales for precipitation, moisture flux convergence, and IWV tendency that is smoothed out when averaging over the full budget region. Across subregions, surface rain rate is linearly proportional to dynamical convergence of water vapor. These observational results improve our understanding of the thermodynamic and kinematic processes that control IWV in atmospheric rivers and the scales at which they occur.

Download Full-text

Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5821-2018 ◽

2018 ◽

Vol 18 (8) ◽

pp. 5821-5846 ◽

Cited By ~ 10

Author(s):

Daniel T. McCoy ◽

Paul R. Field ◽

Anja Schmidt ◽

Daniel P. Grosvenor ◽

Frida A.-M. Bender ◽

...

Keyword(s):

High Resolution ◽

Rain Rate ◽

Cloud Droplet ◽

Moisture Flux ◽

Conveyor Belt ◽

Liquid Water Path ◽

Aerosol Cloud ◽

Cloud Properties ◽

The Difference ◽

Aerosol Cloud Interactions

Abstract. Aerosol–cloud interactions are a major source of uncertainty in inferring the climate sensitivity from the observational record of temperature. The adjustment of clouds to aerosol is a poorly constrained aspect of these aerosol–cloud interactions. Here, we examine the response of midlatitude cyclone cloud properties to a change in cloud droplet number concentration (CDNC). Idealized experiments in high-resolution, convection-permitting global aquaplanet simulations with constant CDNC are compared to 13 years of remote-sensing observations. Observations and idealized aquaplanet simulations agree that increased warm conveyor belt (WCB) moisture flux into cyclones is consistent with higher cyclone liquid water path (CLWP). When CDNC is increased a larger LWP is needed to give the same rain rate. The LWP adjusts to allow the rain rate to be equal to the moisture flux into the cyclone along the WCB. This results in an increased CLWP for higher CDNC at a fixed WCB moisture flux in both observations and simulations. If observed cyclones in the top and bottom tercile of CDNC are contrasted it is found that they have not only higher CLWP but also cloud cover and albedo. The difference in cyclone albedo between the cyclones in the top and bottom third of CDNC is observed by CERES to be between 0.018 and 0.032, which is consistent with a 4.6–8.3 Wm−2 in-cyclone enhancement in upwelling shortwave when scaled by annual-mean insolation. Based on a regression model to observed cyclone properties, roughly 60 % of the observed variability in CLWP can be explained by CDNC and WCB moisture flux.

Download Full-text

Assessing Future Changes in the East Asian Summer Monsoon Using CMIP5 Coupled Models

Journal of Climate ◽

10.1175/jcli-d-12-00694.1 ◽

2013 ◽

Vol 26 (19) ◽

pp. 7662-7675 ◽

Cited By ~ 71

Author(s):

Kyong-Hwan Seo ◽

Jung Ok ◽

Jun-Hyeok Son ◽

Dong-Hyun Cha

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Moisture Flux ◽

Moisture Convergence ◽

Cmip5 Models ◽

Moisture Flux Convergence ◽

The North ◽

Asian Summer

Abstract Future changes in the East Asian summer monsoon (EASM) are estimated from historical and Representative Concentration Pathway 6.0 (RCP6) experiments of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The historical runs show that, like the CMIP3 models, the CMIP5 models produce slightly smaller precipitation. A moisture budget analysis illustrates that this precipitation deficit is due to an underestimation in evaporation and ensuing moisture flux convergence. Of the two components of the moisture flux convergence (i.e., moisture convergence and horizontal moist advection), moisture convergence associated with mass convergence is underestimated to a greater degree. Precipitation is anticipated to increase by 10%–15% toward the end of the twenty-first century over the major monsoonal front region. A statistically significant increase is predicted to occur mostly over the Baiu region and to the north and northeast of the Korean Peninsula. This increase is attributed to an increase in evaporation and moist flux convergence (with enhanced moisture convergence contributing the most) induced by the northwestward strengthening of the North Pacific subtropical high (NPSH), a characteristic feature of the future EASM that occurred in CMIP5 simulations. Along the northern and northwestern flank of the strengthened NPSH, intensified southerly or southwesterly winds lead to the increase in moist convergence, enhancing precipitation over these areas. However, future precipitation over the East China Sea is projected to decrease. In the EASM domain, a local mechanism prevails, with increased moisture and moisture convergence leading to a greater increase in moist static energy in the lower troposphere than in the upper troposphere, reducing tropospheric stability.

Download Full-text

Improved rain-rate and drop-size retrievals from airborne and spaceborne Doppler radar

10.5194/acp-2017-280 ◽

2017 ◽

Author(s):

Shannon L. Mason ◽

J. Christine Chiu ◽

Robin J. Hogan ◽

Lin Tian

Keyword(s):

Size Distribution ◽

Drop Size ◽

Rain Rate ◽

Doppler Radar ◽

Number Concentration ◽

Doppler Velocity ◽

Light Rain ◽

Warm Rain ◽

Rain Drop ◽

Drop Number

Abstract. Satellite radar remote-sensing of rain is important for quantifying of the global hydrological cycle, atmospheric energy budget, and many microphysical cloud and precipitation processes; however, radar estimates of rain rate are sensitive to assumptions about the raindrop size distribution. The upcoming EarthCARE satellite will feature a 94-GHz Doppler radar alongside lidar and radiometer instruments, presenting opportunities for enhanced global retrievals of the rain drop size distribution. In this paper we demonstrate the capability to retrieve both rain rate and a parameter of the rain drop size distribution from an airborne 94-GHz Doppler radar using CAPTIVATE, the variational retrieval algorithm developed for EarthCARE radar–lidar synergy. For a range of rain regimes observed during the Tropical Composition, Cloud and Climate Coupling (TC4) field campaign in the eastern Pacific in 2007, we explore the contributions of Doppler velocity and path-integrated attenuation (PIA) to the retrievals, and evaluate the retrievals against independent measurements from a second, less attenuated, Doppler radar aboard the same aircraft. Retrieved drop number concentration varied over five orders of magnitude between light rain from melting ice, and warm rain from liquid clouds. Doppler velocity can be used to estimate rain rate over land, and retrievals of rain rate and drop number concentration are possible in profiles of light rain over land; in moderate warm rain, drop number concentration can be retrieved without Doppler velocity. These results suggest that EarthCARE rain retrievals facilitated by Doppler radar will make substantial improvements to the global understanding of the interaction of clouds and precipitation.

Download Full-text

Summertime precipitation in Hokkaido and Kyushu, Japan in response to global warming

10.21203/rs.3.rs-286237/v1 ◽

2021 ◽

Author(s):

Daichi Takabatake ◽

Masaru Inatsu

Keyword(s):

Global Warming ◽

Tropical Cyclones ◽

General Circulation ◽

Dynamical Downscaling ◽

Circulation Model ◽

Policy Decision ◽

Moisture Flux ◽

Specific Humidity ◽

Future Climate Change ◽

Moisture Flux Convergence

Abstract We analyzed a large ensemble dataset called the database for Policy Decision Making for Future climate change (d4PDF), which contains 60-km resolution atmospheric general circulation model output and 20-km resolution dynamical downscaling for the Japanese domain. The increase in moisture and precipitation, and their global warming response in June–July–August were described focusing on the differences between Hokkaido and Kyushu. The results suggested that the specific humidity increased almost following the Clausius Clapeyron relation, but the change in stationary circulation suppressed the precipitation increase, except for in western Kyushu. The + 4 K climate in Hokkaido would be as hot and humid as the present climate in Kyushu. The circulation change related to the southward shift of the jet stream and an eastward shift of the Bonin high weakened the moisture flux convergence via a stationary field over central Japan including eastern Kyushu. The transient eddy activity counteracted the increase in humidity, so that the moisture flux convergence and precipitation did not change much over Hokkaido. Because the contribution of tropical cyclones to the total precipitation was at most 10%, the decrease in the number of tropical cyclones did not explain the predicted change in precipitation.

Download Full-text

Frequency of deep convective clouds in the tropical zone from ten years of AIRS data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-10009-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 10009-10047

Author(s):

H. H. Aumann ◽

A. Ruzmaikin

Keyword(s):

Water Vapor ◽

Brightness Temperature ◽

Frequency Of Occurrence ◽

Tropical Zone ◽

Convective Clouds ◽

Atmospheric Window ◽

Deep Convective Clouds ◽

Sst Anomaly ◽

The Difference ◽

Global Precipitation

Abstract. Deep Convective Clouds (DCC) have been widely studied because of their association with heavy precipitation and severe weather events. To identify DCC with Atmospheric Infrared Sounder (AIRS) data we use three types of thresholds: (1) thresholds based on the absolute value of an atmospheric window channel brightness temperature; (2) thresholds based on the difference between the brightness temperature in an atmospheric window channel and the brightness temperature centered on a strong water vapor absorption line; and (3) a threshold using the difference between the window channel brightness temperature and the tropopause temperature based on climatology. We find that DCC identified with threshold (2) (referred to as DCCw4) cover 0.16% of the area of the tropical zone and 72% of them are identified as deep convective, 39% are overshooting based on simultaneous observations with the Advanced Microwave Sounding Unit-HSB (AMSU-HSB) 183 GHz water vapor channels. In the past ten years the frequency of occurrence of DCC decreased for the tropical ocean, while it increased for tropical land. The land increase-ocean decrease closely balance, such that the DCC frequency changed at an insignificant rate for the entire tropical zone. This pattern of essentially zero trend for the tropical zone, but opposite land/ocean trends, is consistent with measurements of global precipitation. The changes in frequency of occurrence of the DCC are correlated with the Niño34 index, which defines the SST anomaly in the East-Central Pacific. This is also consistent with patterns seen in global precipitation. This suggests that the observed changes in the frequency are part of a decadal variability characterized by shifts in the main tropical circulation patterns, which does not fully balance in the ten year AIRS data record. The regional correlations and anti-correlations of the DCC frequency anomaly with the Multivariate ENSO Index (MEI) provides a new perspective for the regional analysis of past events, since the SST anomaly in the Nino34 region is available in the form of the extended MEI since 1871. Depending on the selected threshold, the frequency of DCC in the tropical zone ranges from 0.06% to 0.8% of the area. We find that the least frequent, more extreme DCC also show the largest trend in frequency, increasing over land, decreasing over ocean. This finding fits into the framework of how weather extremes respond to climate change.

Download Full-text

Retrieval of Cloud Water and Water Vapor Contents from Doppler Radar Data in a Tropical Squall Line

Journal of the Atmospheric Sciences ◽

10.1175/1520-0469(1986)043<0823:rocwaw>2.0.co;2 ◽

1986 ◽

Vol 43 (8) ◽

pp. 823-838 ◽

Cited By ~ 26

Author(s):

Danièle Hauser ◽

Paul Amayenc

Keyword(s):

Water Vapor ◽

Doppler Radar ◽

Radar Data ◽

Cloud Water ◽

Squall Line ◽

Doppler Radar Data

Download Full-text

The Aftermath

Impact! ◽

10.1093/oso/9780195101058.003.0018 ◽

1996 ◽

Author(s):

Gerrit L. Verschuur

Keyword(s):

Water Vapor ◽

Spectral Line ◽

Asteroid Impact ◽

Infrared Telescope ◽

University Of Arizona ◽

The Difference ◽

Life On Earth ◽

The University ◽

The Impact ◽

Space Telescope Science Institute

After all the hoopla associated with Jupiter’s publicity stunt died down, planetary scientists got down to the business of analyzing their data. Simulations of the aftermath of a comet or asteroid impact had been available for years and in July 1994 many of the predictions were confirmed, albeit some more dramatically than expected. The timing of the event was almost as if to remind us to take more seriously what we have been thinking and talking about for some time. Putting aside for a moment the implications for life on earth had something similar happened here, let’s look at some of the things that were learned. Argument continues as to what actually hit Jupiter, a comet or asteroid. When the Space Telescope Science Institute sent out a press release on September 29, 1994, entitled “Hubble Observations Shed New Light on Jupiter Collision,” we were led to expect an answer. The introduction gave us further hope: “Was it a comet or an asteroid?” But the institute didn’t have the answer. Its observations slightly favored a cometary origin, but the asteroid possibility still could not be ruled out. Comets are mostly icy, or so we like to think, and asteroids are mostly rocky or metallic, or so we like to think. When you really get down to it, this business of the difference between comets and asteroids has launched a new cottage industry within astronomical circles. A more recent hint that a comet was involved came from observations made from on board the Kuiper Airborne Observatory, an airplane that carries a beautiful infrared telescope high above most of the water vapor in the atmosphere where it can then see more clearly. Ann Sprague and Donald Huntern from the University of Arizona and their colleagues found evidence for water minutes after two of the fragments smashed into Jupiter. The water signature, a spectral line, indicated it was at a temperature of 500 kelvins (degrees above absolute zero, or about 230 Celcius), much hotter than Jupiter’s usual 200 kelvins (-73 Celcius). Although they could not rule out that the water originated deep in Jupiter’s clouds, the way it came and went over a period of 20 minutes suggested that it was liberated by the impact and was part of a cometlike object.

Download Full-text

Coupling of Precipitation and Cloud Structures in Oceanic Extratropical Cyclones to Large-Scale Moisture Flux Convergence

Journal of Climate ◽

10.1175/jcli-d-18-0115.1 ◽

2018 ◽

Vol 31 (23) ◽

pp. 9565-9584 ◽

Cited By ~ 3

Author(s):

Sun Wong ◽

Catherine M. Naud ◽

Brian H. Kahn ◽

Longtao Wu ◽

Eric J. Fetzer

Keyword(s):

Large Scale ◽

Moisture Flux ◽

Extratropical Cyclones ◽

Flux Divergence ◽

Moisture Flux Convergence ◽

Convective Clouds ◽

Moisture Advection ◽

Deep Convective Clouds ◽

Stratiform Clouds ◽

High Level

Precipitation (from TMPA) and cloud structures (from MODIS) in extratropical cyclones (ETCs) are modulated by phases of large-scale moisture flux convergence (from MERRA-2) in the sectors of ETCs, which are studied in a new coordinate system with directions of both surface warm fronts (WFs) and surface cold fronts (CFs) fixed. The phase of moisture flux convergence is described by moisture dynamical convergence Qcnvg and moisture advection Qadvt. Precipitation and occurrence frequencies of deep convective clouds are sensitive to changes in Qcnvg, while moisture tendency is sensitive to changes in Qadvt. Increasing Qcnvg and Qadvt during the advance of the WF is associated with increasing occurrences of both deep convective and high-level stratiform clouds. A rapid decrease in Qadvt with a relatively steady Qcnvg during the advance of the CF is associated with high-level cloud distribution weighting toward deep convective clouds. Behind the CF (cold sector or area with polar air intrusion), the moisture flux is divergent with abundant low- and midlevel clouds. From deepening to decaying stages, the pre-WF and WF sectors experience high-level clouds shifting to more convective and less stratiform because of decreasing Qadvt with relatively steady Qcnvg, and the CF experiences shifting from high-level to midlevel clouds. Sectors of moisture flux divergence are less influenced by cyclone evolution. Surface evaporation is the largest in the cold sector and the CF during the deepening stage. Deepening cyclones are more efficient in poleward transport of water vapor.

Download Full-text