scholarly journals The Mass of the Atmosphere: A Constraint on Global Analyses

2005 ◽  
Vol 18 (6) ◽  
pp. 864-875 ◽  
Author(s):  
Kevin E. Trenberth ◽  
Lesley Smith
Keyword(s):  
Water Vapor ◽  
Surface Pressure ◽  
Total Mass ◽  
Precipitable Water ◽  
Atmospheric Composition ◽  
Specific Humidity ◽  
Air Mass ◽  
Dry Air ◽  
Annual Range ◽  
Global Mean

Abstract The total mass of the atmosphere varies mainly from changes in water vapor loading; the former is proportional to global mean surface pressure and the water vapor component is computed directly from specific humidity and precipitable water using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analyses (ERA-40). Their difference, the mass of the dry atmosphere, is estimated to be constant for the equivalent surface pressure to within 0.01 hPa based on changes in atmospheric composition. Global reanalyses satisfy this constraint for monthly means for 1979–2001 with a standard deviation of 0.065 hPa. New estimates of the total mass of the atmosphere and its dry component, and their corresponding surface pressures, are larger than previous estimates owing to new topography of the earth’s surface that is 5.5 m lower for the global mean. Global mean total surface pressure is 985.50 hPa, 0.9 hPa higher than previous best estimates. The total mean mass of the atmosphere is 5.1480 × 1018 kg with an annual range due to water vapor of 1.2 or 1.5 × 1015 kg depending on whether surface pressure or water vapor data are used; this is somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27 × 1016 kg and the dry air mass as 5.1352 ± 0.0003 × 1018 kg. The water vapor contribution varies with an annual cycle of 0.29-hPa, a maximum in July of 2.62 hPa, and a minimum in December of 2.33 hPa, although the total global surface pressure has a slightly smaller range. During the 1982/83 and 1997/98 El Niño events, water vapor amounts and thus total mass increased by about 0.1 hPa in surface pressure or 0.5 × 1015 kg for several months. Some evidence exists for slight decreases following the Mount Pinatubo eruption in 1991 and also for upward trends associated with increasing global mean temperatures, but uncertainties due to the changing observing system compromise the evidence. The physical constraint of conservation of dry air mass is violated in the reanalyses with increasing magnitude prior to the assimilation of satellite data in both ERA-40 and the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalyses. The problem areas are shown to occur especially over the Southern Oceans. Substantial spurious changes are also found in surface pressures due to water vapor, especially in the Tropics and subtropics prior to 1979.

scholarly journals Assessment of Regional Global Climate Model Water Vapor Bias and Trends Using Precipitable Water Vapor (PWV) Observations from a Network of Global Positioning Satellite (GPS) Receivers in the U.S. Great Plains and Midwest

2012 ◽  
Vol 25 (16) ◽  
pp. 5471-5493 ◽  
Author(s):  
Jacola A. Roman ◽  
Robert O. Knuteson ◽  
Steven A. Ackerman ◽  
David C. Tobin ◽  
Henry E. Revercomb
Keyword(s):  
Water Vapor ◽  
Great Plains ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Precipitable Water ◽  
Specific Humidity ◽  
Model Output ◽  
Global Positioning ◽  
The U.S

Abstract Precipitable water vapor (PWV) observations from the National Center of Atmospheric Research (NCAR) SuomiNet networks of ground-based global positioning system (GPS) receivers and the National Oceanic and Atmospheric Administration (NOAA) Profiler Network (NPN) are used in the regional assessment of global climate models. Study regions in the U.S. Great Plains and Midwest highlight the differences among global climate model output from the Fourth Assessment Report (AR4) Special Report on Emissions Scenarios (SRES) A2 scenario in their seasonal representation of column water vapor and the vertical distribution of moisture. In particular, the Community Climate System model, version 3 (CCSM3) is shown to exhibit a dry bias of over 30% in the summertime water vapor column, while the Goddard Institute for Space Studies Model E20 (GISS E20) agrees well with PWV observations. A detailed assessment of vertical profiles of temperature, relative humidity, and specific humidity confirm that only GISS E20 was able to represent the summertime specific humidity profile in the atmospheric boundary layer (<3%) and thus the correct total column water vapor. All models show good agreement in the winter season for the region. Regional trends using station-elevation-corrected GPS PWV data from two complimentary networks are found to be consistent with null trends predicted in the AR4 A2 scenario model output for the period 2000–09. The time to detect (TTD) a 0.05 mm yr−1 PWV trend, as predicted in the A2 scenario for the period 2000–2100, is shown to be 25–30 yr with 95% confidence in the Oklahoma–Kansas region.

scholarly journals An ERA5-Based Hourly Global Pressure and Temperature (HGPT) Model

2020 ◽  
Vol 12 (7) ◽  
pp. 1098
Author(s):  
Pedro Mateus ◽  
João Catalão ◽  
Virgílio B. Mendes ◽  
Giovanni Nico
Keyword(s):  
Water Vapor ◽  
Air Temperature ◽  
Surface Pressure ◽  
Surface Air Temperature ◽  
Precipitable Water ◽  
Weighted Mean ◽  
Zenith Wet Delay ◽  
Mean Temperature ◽  
Weighted Mean Temperature ◽  
Zenith Hydrostatic Delay

The Global Navigation Satellite System (GNSS) meteorology contribution to the comprehension of the Earth’s atmosphere’s global and regional variations is essential. In GNSS processing, the zenith wet delay is obtained using the difference between the zenith total delay and the zenith hydrostatic delay. The zenith wet delay can also be converted into precipitable water vapor by knowing the atmospheric weighted mean temperature profiles. Improving the accuracy of the zenith hydrostatic delay and the weighted mean temperature, normally obtained using modeled surface meteorological parameters at coarse scales, leads to a more accurate and precise zenith wet delay estimation, and consequently, to a better precipitable water vapor estimation. In this study, we developed an hourly global pressure and temperature (HGPT) model based on the full spatial and temporal resolution of the new ERA5 reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The HGPT model provides information regarding the surface pressure, surface air temperature, zenith hydrostatic delay, and weighted mean temperature. It is based on the time-segmentation concept and uses the annual and semi-annual periodicities for surface pressure, and annual, semi-annual, and quarterly periodicities for surface air temperature. The amplitudes and initial phase variations are estimated as a periodic function. The weighted mean temperature is determined using a 20-year time series of monthly data to understand its seasonality and geographic variability. We also introduced a linear trend to account for a global climate change scenario. Data from the year 2018 acquired from 510 radiosonde stations downloaded from the National Oceanic and Atmospheric Administration (NOAA) Integrated Global Radiosonde Archive were used to assess the model coefficients. Results show that the GNSS meteorology, hydrological models, Interferometric Synthetic Aperture Radar (InSAR) meteorology, climate studies, and other topics can significantly benefit from an ERA5 full-resolution model.

scholarly journals <i>A Tale of Two Dust Storms</i>: analysis of a complex dust event in the Middle East

2019 ◽  
Vol 12 (9) ◽  
pp. 5101-5118 ◽  
Author(s):  
Steven D. Miller ◽  
Louie D. Grasso ◽  
Qijing Bian ◽  
Sonia M. Kreidenweis ◽  
Jack F. Dostalek ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mineral Dust ◽  
Weather Prediction ◽  
Detection Threshold ◽  
Dust Storms ◽  
Moist Air ◽  
Air Mass ◽  
Dry Air ◽  
Environmental Controls ◽  
Dust Detection

Abstract. Lofted mineral dust over data-sparse regions presents considerable challenges to satellite-based remote sensing methods and numerical weather prediction alike. The southwest Asia domain is replete with such examples, with its diverse array of dust sources, dust mineralogy, and meteorologically driven lofting mechanisms on multiple spatial and temporal scales. A microcosm of these challenges occurred over 3–4 August 2016 when two dust plumes, one lofted within an inland dry air mass and another embedded within a moist air mass, met over the southern Arabian Peninsula. Whereas conventional infrared-based techniques readily detected the dry air mass dust plume, they experienced marked difficulties in detecting the moist air mass dust plume, becoming apparent when visible reflectance revealed the plume crossing over an adjacent dark water background. In combining information from numerical modeling, multi-satellite and multi-sensor observations of lofted dust and moisture profiles, and idealized radiative transfer simulations, we develop a better understanding of the environmental controls of this event, characterizing the sensitivity of infrared-based dust detection to column water vapor, dust vertical extent, and dust optical properties. Differences in assumptions of dust complex refractive index translate to variations in the sign and magnitude of the split-window brightness temperature difference commonly used for detecting mineral dust. A multi-sensor technique for mitigating the radiative masking effects of water vapor via modulation of the split-window dust-detection threshold, predicated on idealized simulations tied to these driving factors, is proposed and demonstrated. The new technique, indexed to an independent description of the surface-to-500 hPa atmospheric column moisture, reveals parts of the missing dust plume embedded in the moist air mass, with the best performance realized over land surfaces.

scholarly journals Stratospheric ozone changes under solar geoengineering: implications for UV exposure and air quality

2016 ◽  
Vol 16 (6) ◽  
pp. 4191-4203 ◽  
Author(s):  
Peer Johannes Nowack ◽  
Nathan Luke Abraham ◽  
Peter Braesicke ◽  
John Adrian Pyle
Keyword(s):  
Air Quality ◽  
Atmospheric Carbon Dioxide ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Atmospheric Composition ◽  
Specific Humidity ◽  
Uv Exposure ◽  
Solar Radiation Management ◽  
Global Mean

Abstract. Various forms of geoengineering have been proposed to counter anthropogenic climate change. Methods which aim to modify the Earth's energy balance by reducing insolation are often subsumed under the term solar radiation management (SRM). Here, we present results of a standard SRM modelling experiment in which the incoming solar irradiance is reduced to offset the global mean warming induced by a quadrupling of atmospheric carbon dioxide. For the first time in an atmosphere–ocean coupled climate model, we include atmospheric composition feedbacks for this experiment. While the SRM scheme considered here could offset greenhouse gas induced global mean surface warming, it leads to important changes in atmospheric composition. We find large stratospheric ozone increases that induce significant reductions in surface UV-B irradiance, which would have implications for vitamin D production. In addition, the higher stratospheric ozone levels lead to decreased ozone photolysis in the troposphere. In combination with lower atmospheric specific humidity under SRM, this results in overall surface ozone concentration increases in the idealized G1 experiment. Both UV-B and surface ozone changes are important for human health. We therefore highlight that both stratospheric and tropospheric ozone changes must be considered in the assessment of any SRM scheme, due to their important roles in regulating UV exposure and air quality.

The Atmospheric Energy Constraint on Global-Mean Precipitation Change

2014 ◽  
Vol 27 (2) ◽  
pp. 757-768 ◽  
Author(s):  
Angeline G. Pendergrass ◽  
Dennis L. Hartmann
Keyword(s):  
Water Vapor ◽  
Temperature Increase ◽  
Longwave Radiation ◽  
Surface Fluxes ◽  
Lapse Rate ◽  
Specific Humidity ◽  
Radiative Cooling ◽  
Rate Of Increase ◽  
Precipitation Increase ◽  
Global Mean

Abstract Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) robustly predict that the rate of increase in global-mean precipitation with global-mean surface temperature increase is much less than the rate of increase of water vapor. The goal of this paper is to explain in detail the mechanisms by which precipitation increase is constrained by radiative cooling. Changes in clear-sky atmospheric radiative cooling resulting from changes in temperature and humidity in global warming simulations are in good agreement with the multimodel, global-mean precipitation increase projected by GCMs (~1.1 W m−2 K−1). In an atmosphere with fixed specific humidity, radiative cooling from the top of the atmosphere (TOA) increases in response to a uniform temperature increase of the surface and atmosphere, while atmospheric cooling by exchange with the surface decreases because the upward emission of longwave radiation from the surface increases more than the downward longwave radiation from the atmosphere. When a fixed relative humidity (RH) assumption is made, however, uniform warming causes a much smaller increase of cooling at the TOA, and the surface contribution reverses to an increase in net cooling rate due to increased downward emission from water vapor. Sensitivity of precipitation changes to lapse rate changes is modest when RH is fixed. Carbon dioxide reduces TOA emission with only weak effects on surface fluxes, and thus suppresses precipitation. The net atmospheric cooling response and thereby the precipitation response to CO2-induced warming at fixed RH are mostly contributed by changes in surface fluxes. The role of clouds is discussed. Intermodel spread in the rate of precipitation increase across the CMIP5 simulations is attributed to differences in the atmospheric cooling.

scholarly journals Determination of zenith hydrostatic delays and the development of new global long-term GNSS-derived precipitable water vapor

2016 ◽  
Author(s):  
Xiaoming Wang ◽  
Kefei Zhang ◽  
Suqin Wu ◽  
Changyong He ◽  
Yingyan Cheng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Surface Pressure ◽  
Meteorological Data ◽  
Accurate Determination ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Global Navigation Satellite Systems ◽  
Average Value ◽  
Rms Errors

Abstract. Surface pressure is a vital meteorological variable for the accurate determination of precipitable water vapor (PWV) using Global Navigation Satellite Systems (GNSS). The lack of pressure observations is a big issue for the study of climate using historical GNSS observations, which is a relatively new area of GNSS applications in climatology. Hence the use of the surface pressure derived from either an empirical model (e.g. Global Pressure and Temperature 2 wet, GPT2w) or a global atmospheric reanalysis (e.g. ERA-Interim) becomes an important alternative solution. In this study, pressure derived from these two methods is compared against the pressure observed at 108 global GNSS stations for the period 2000–2013. Results show that a good accuracy is achieved from the GPT2w-derived pressure in the latitude band of −30 to 30° and the average value of Root-Mean-Square (RMS) errors across all the stations in this region is 2.4 mb. Correspondingly, an error of 5.6 mm and 1.0 mm in its resultant zenith hydrostatic delay (ZHD) and PWV is expected. In addition, GPT2w-derived pressure usually has a larger error in the cold season due to large diurnal ranges, which is not considered in the GPT2w model. The average value of the RMS errors of the ERA-Interim-derived pressure across all the 108 stations is 1.1 mb, which will lead to an equivalent error of 2.5 mm and 0.4 mm in its resultant ZHD and PWV respectively. Our research also indicates that the ERA-Interim-derived pressure has the potential to be used as a useful meteorological data source to obtain high accuracy PWV on a global scale for climate studies and the GPT2w-derived pressure can be potentially used for climatology as well although it may be only suitable for the tropical regions.

scholarly journals Estimation of the Precipitable Water and Water Vapor Fluxes in the Coastal and Inland Cities of China Using MAX-DOAS

2021 ◽  
Vol 13 (9) ◽  
pp. 1675
Author(s):  
Hongmei Ren ◽  
Ang Li ◽  
Pinhua Xie ◽  
Zhaokun Hu ◽  
Jin Xu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Vapor ◽  
Precipitable Water ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Continuous Precipitation ◽  
Air Mass ◽  
Torrential Rain ◽  
Two Cities ◽  
High Level

Water vapor transport affects regional precipitation and climate change. The measurement of precipitable water (PW) and water vapor flux (WVF) is of great importance for the study of precipitation and water vapor transport. This study presented a new method of computing PW and estimating WVF using the water vapor vertical column density (VCD) and profile retrieved from multi-axis differential optical absorption spectroscopy (MAX-DOAS), combined with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 wind profiles. We applied our method to MAX-DOAS observations in the coastal (Qingdao) and inland (Xi’an) cities of China from June 2019 to May 2020 and compared the results to the ERA5 reanalysis datasets. Good agreement with ERA5 datasets was found; the correlation coefficient (r) of the PW and the zonal and meridional WVFs were r ≥ 0.92, r = 0.77, and r ≥ 0.89, respectively. The comparison results showed the feasibility and reliability of estimating PW and WVF using MAX-DOAS. Then, we analyzed the seasonal and diurnal climatology of the PW and WVFs in Qingdao and Xi’an. The results indicated that the seasonal and diurnal variations of the PW in the two cities were similar. The zonal water vapor transport of the two cities mainly involved eastward transport, Qingdao’s meridional water vapor mainly involved southward transport, and that of Xi’an mainly involved northward transport. The WVFs of the two cities were higher in the afternoon than in the morning, which may be related to wind speed. The results also indicated that the WVF transmitting belts appeared at around 2 and 1.4 km above the surface in Qingdao and around 2.8, 2.6, 1.6, and 1.0 km above the surface in Xi’an. Before precipitation, the WVF transmitting belt moved from near the ground to a high level, reaching its maximum at about 2 km, and the PW and meridional vertically integrated WVF increased. Finally, the sources and transports of water vapor during continuous precipitation and torrential rain were analyzed according to a 24 h backward trajectory. The air mass from the southeast accounted for more than 84% during continuous precipitation in Xi’an, while the air mass from the ocean accounted for more than 75% during torrential rain in Qingdao and was accompanied by a high-level ocean jet stream. As an optical remote sensing instrument, MAX-DOAS has the advantages of high spatiotemporal resolution, low cost, and easy maintenance. The application of MAX-DOAS to meteorological remote sensing provides a better method for evaluating the PW and WVF.

scholarly journals Subseasonal Variations of Wintertime North Pacific Evaporation, Cold Air Surges, and Water Vapor Transport

2017 ◽  
Vol 30 (23) ◽  
pp. 9475-9491 ◽  
Author(s):  
Xuejuan Ren ◽  
Xiu-Qun Yang ◽  
Haibo Hu
Keyword(s):  
Water Vapor ◽  
North Pacific ◽  
Wave Train ◽  
Vapor Transport ◽  
Specific Humidity ◽  
Water Vapor Transport ◽  
Vapor Source ◽  
Air Mass ◽  
Cold Air ◽  
The North

This study addresses subseasonal variations of oceanic evaporation E over the North Pacific during winter and the connection with the cold air surges (CASs) and atmospheric water vapor transport using the OAFlux and ERA-Interim daily data. By performing an empirical orthogonal function (EOF) analysis, two dominant modes of subseasonal evaporation anomaly E′ are identified: a zonal wave train–like pattern (EOF1) and an east negative–west positive dipolar pattern (EOF2) in the midlatitude basin. Further analyses yield the following conclusions. 1) The Siberian high (SH)-related CAS has a crucial role in generation of the EOF1 mode of E′. When the dry and cold air mass passes the region of the warm Kuroshio and its extension [Kuroshio–Oyashio Extension (KOE)], the increased air–sea temperature and moisture differences and intensified wind speed lead to the above-normal oceanic E, and vice versa. 2) The Aleutian low (AL)-related CAS contributes to the EOF2 mode of E′. The intensified AL transports a dramatically colder and drier air mass toward the KOE region and a slightly warmer and wetter one toward the west coast of North America, leading to the east negative–west positive structure of E′ in the midlatitude basin. 3) A quasi-linear relationship exists between E′ and divergent water vapor transport anomalies over the KOE region. Positive (negative) E′ is generally accompanied by anomalous vapor source (sink). 4) The divergent water vapor transport anomalies associated with the two EOFs are preliminarily decided by their individual lower-level wind field anomalies and second by the meridional inhomogeneity of subseasonal specific humidity anomalies. Hydroclimate effects on precipitation over the pan–North Pacific region are also discussed.

scholarly journals Diurnal Cycle of Convective Instability around the Central Mountains in Japan during the Warm Season

2005 ◽  
Vol 62 (5) ◽  
pp. 1626-1636 ◽  
Author(s):  
Tomonori Sato ◽  
Fujio Kimura
Keyword(s):  
Water Vapor ◽  
Diurnal Cycle ◽  
Convective Instability ◽  
Potential Temperature ◽  
Warm Season ◽  
Precipitable Water ◽  
Specific Humidity ◽  
High Temporal Resolution ◽  
Mountainous Areas ◽  
Diurnal Cycles

Abstract Convective rainfall often shows a clear diurnal cycle. The nighttime peak of convective activity prevails in various regions near the world's mountains. The influence of the water vapor and convective instability upon nocturnal precipitation is investigated using a numerical model and observed data. Recent developments in GPS meteorology allow the estimation of precipitable water vapor (PWV) with a high temporal resolution. A dense network has been established in Japan. The GPS analysis in August 2000 provides the following results: In the early evening, a high-GPS-PWV region forms over mountainous areas because of the convergence of low-level moisture, which gradually propagates toward the adjacent plain before midnight. A region of convection propagates simultaneously eastward into the plain. The precipitating frequency correlates fairly well with the GPS-PWV and attains a maximum value at night over the plain. The model also provides similar characteristics in the diurnal cycles of rainfall and high PWV. Abundant moisture accumulates over the mountainous areas in the afternoon and then advects continuously toward the plain by the ambient wind. The specific humidity greatly increases at about the 800-hPa level over the plain at night, and the PWV reaches its nocturnal maximum. The increase in the specific humidity causes an increase of equivalent potential temperature at about the 800-hPa level; as a result, the convective instability index becomes more unstable over the plain at night. These findings are consistent with the diurnal cycle of the observed precipitating frequency.

scholarly journals Pengaruh Suhu dan Kelembaban Terhadap Rasio Kelembaban dan Entalpi (Studi Kasus: Gedung UNIFA Makassar)

2021 ◽  
pp. 102-114
Author(s):  
Ahmad Nadhil Edar
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Experimental Studies ◽  
Well Being ◽  
Specific Humidity ◽  
Unit Mass ◽  
Specific Enthalpy ◽  
Humidity Ratio ◽  
Total Enthalpy ◽  
Dry Air

Temperature affects humidity. The interaction of temperature and humidity also directly affects the health and well-being of humans. The relative humidity (RH) of the air is an indication of how much water vapor is in the air at a particular temperature compared with how much water vapor the air could actually hold at that temperature. Air at 100 % relative humidity holds the maximum amount of water possible at that particular temperature and is said to be saturated. Therefore, air at 50% relative humidity, regardless of temperature, is holding half of its total possible water capacity. In essence, cold air cannot hold as much water vapor as warm air. In a closed environment such as a display case, there will be a fixed amount of water vapor, referred to as the absolute humidity. If the temperature inside the case falls then the relative humidity will rise. If the temperature rises the relative humidity will fall. Such changes in relative humidity could be caused by many factors including direct sunlight, spotlights and air-conditioning failures. Research carried out by experimental studies that we can get the humidity ratio and specific enthalpy in a kind of rooms either using The Psychrometric Chart and The formula. The specific humidity or humidity ratio of an air sample is the ratio of the weight of water vapor contained in the sample compared to the weight of the dry air in the same sample. Enthalpy is the amount of heat (energy) in the air per unit mass. Enthalpy is the total amount of energy present in the air, both from air and water vapor contained therein. And, Specific enthalpy of moist air is defined as the total enthalpy of the dry air and the water vapor mixture - per unit mass of dry air. Keywords: Temperature; Relative Humidity; Humidity Ratio; Specific Enthalpy.

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