A Graphical Technique of Forecasting Overcast Skies and Precipitation with Central Weather Facility Products

1961 ◽  
Vol 42 (2) ◽  
pp. 110-117 ◽  
Author(s):  
James P. Jenrette
Keyword(s):  
Vertical Motion ◽  
Precipitable Water ◽  
Critical Values ◽  
Motion Field ◽  
Water Field ◽  
Graphical Technique ◽  
Thickness Field

Practical procedures for forecasting areas of overcast skies and precipitation are presented. The forecast thickness field is relabeled as a forecast maximum precipitable water field. A forecast actual precepitable water field is then graphically subtracted from this field to derive a forecast saturation chart. The forecast saturation chart is then adjusted with the forecast vertical-motion field. Isopleths of critical values on the adjusted saturation chart outline forecast areas of overcast skies and areas of probable precipitation.

scholarly journals Dry and moist dynamics shape regional patterns of extreme precipitation sensitivity

2020 ◽  
Vol 117 (16) ◽  
pp. 8757-8763 ◽  
Author(s):  
Ji Nie ◽  
Panxi Dai ◽  
Adam H. Sobel
Keyword(s):  
Global Warming ◽  
Extreme Precipitation ◽  
Large Scale ◽  
Climate Model ◽  
Regional Scale ◽  
Vertical Motion ◽  
Precipitable Water ◽  
Small Scale ◽  
Climate Projections ◽  
Regional Patterns

Responses of extreme precipitation to global warming are of great importance to society and ecosystems. Although observations and climate projections indicate a general intensification of extreme precipitation with warming on global scale, there are significant variations on the regional scale, mainly due to changes in the vertical motion associated with extreme precipitation. Here, we apply quasigeostrophic diagnostics on climate-model simulations to understand the changes in vertical motion, quantifying the roles of dry (large-scale adiabatic flow) and moist (small-scale convection) dynamics in shaping the regional patterns of extreme precipitation sensitivity (EPS). The dry component weakens in the subtropics but strengthens in the middle and high latitudes; the moist component accounts for the positive centers of EPS in the low latitudes and also contributes to the negative centers in the subtropics. A theoretical model depicts a nonlinear relationship between the diabatic heating feedback (α) and precipitable water, indicating high sensitivity of α (thus, EPS) over climatological moist regions. The model also captures the change of α due to competing effects of increases in precipitable water and dry static stability under global warming. Thus, the dry/moist decomposition provides a quantitive and intuitive explanation of the main regional features of EPS.

scholarly journals Synoptic-Scale Dual Structure of Precipitable Water along the Eastern Pacific ITCZ

2014 ◽  
Vol 27 (16) ◽  
pp. 6288-6304 ◽  
Author(s):  
Guanghua Chen ◽  
Yukari N. Takayabu ◽  
Chie Yokoyama
Keyword(s):  
Vertical Structure ◽  
Deep Convection ◽  
Vertical Motion ◽  
Precipitable Water ◽  
Meridional Wind ◽  
Eastern Pacific ◽  
Boreal Summer ◽  
Synoptic Scale ◽  
The West ◽  
Dual Structure

Abstract Using 10-yr high-resolution satellite and reanalysis data, the synoptic-scale dual structure of precipitable water (PW), in which the southern and northern bands straddled at the ITCZ produce zonally propagating meridional dipoles, is observed over the eastern Pacific (EP) during boreal summer and fall. Composites indicate that the PW dipole, concurrent with the dipole-like filtered divergence, has a shift to the west of the anomalously cyclonic circulation. The vertical structure of filtered meridional wind is characterized by a wavenumber-1 baroclinic mode, and the vertical motion has two peaks situated at 850 and 300 hPa, respectively. To the east of the PW dipole, the shallow convection is embedded within the deep convection, forming a multilevel structure of meridional wind on the ITCZ equatorward side. To the west of the PW dipole, the deep convection tends to be suppressed because of the invasion of midlevel dry air advected by northerly flows. The generation and propagation of the dual PW band can be attributed to the divergence and advection terms related to specific humidity and three-dimensional wind. By comparison, the PW anomalies over the western North Pacific, only exhibiting a single band, coincide with the centers of synoptic disturbances with a barotropic vertical structure. Because of the weakening of lower-level divergence, the vertical motion, and the horizontal gradient of PW, the synoptic-scale PW signal is reduced significantly. The typical cases and statistics confirm that the strong meridional dipoles and westward-propagating disturbances are closely associated with the distortion and breakdown of ITCZ over the EP.

The Role of Shearwise and Transverse Quasigeostrophic Vertical Motions in the Midlatitude Cyclone Life Cycle

2006 ◽  
Vol 134 (4) ◽  
pp. 1174-1193 ◽  
Author(s):  
Jonathan E. Martin
Keyword(s):  
Life Cycle ◽  
Vertical Motion ◽  
Development Stage ◽  
Life Cycles ◽  
Vertical Shear ◽  
Mature Stage ◽  
Motion Field ◽  
Initial Development ◽  
Frontal Zones ◽  
Oriented Parallel

Abstract The total quasigeostrophic (QG) vertical motion field is partitioned into transverse and shearwise couplets oriented parallel to, and along, the geostrophic vertical shear, respectively. The physical role played by each of these components of vertical motion in the midlatitude cyclone life cycle is then illustrated by examination of the life cycles of two recently observed cyclones. The analysis suggests that the origin and subsequent intensification of the lower-tropospheric cyclone responds predominantly to column stretching associated with the updraft portion of the shearwise QG vertical motion, which displays a single, dominant, middle-tropospheric couplet at all stages of the cyclone life cycle. The transverse QG omega, associated with the cyclones’ frontal zones, appears only after those frontal zones have been established. The absence of transverse ascent maxima and associated column stretching in the vicinity of the surface cyclone center suggests that the transverse ω plays little role in the initial development stage of the storms examined here. Near the end of the mature stage of the life cycle, however, in what appears to be a characteristic distribution, a transverse ascent maximum along the western edge of the warm frontal zone becomes superimposed with the shearwise ascent maximum that fuels continued cyclogenesis. It is suggested that use of the shearwise/transverse diagnostic approach may provide new and/or supporting insight regarding a number of synoptic processes including the development of upper-level jet/front systems and the nature of the physical distinction between type A and type B cyclogenesis events.

Vertical Motion Inputs for Seismic Analysis of Large Span Bridge

2013 ◽  
Vol 275-277 ◽  
pp. 1403-1406
Author(s):  
Zheng Ru Tao ◽  
Xia Xin Tao
Keyword(s):  
Seismic Analysis ◽  
Three Dimensional ◽  
Low Frequency ◽  
Vertical Motion ◽  
Vertical Acceleration ◽  
Motion Field ◽  
Large Span ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Main Girder

In seismic analysis of large span bridge, inconsistent ground motions in three directions, lengthwise, lateral and vertical are required to input at the base of each of the two main girder piers. In order to adopt synthesized motion field for the inputs, a simple way to prepare the vertical motion is introduced for improvisation at this moment in this paper, since the synthesis in general consists of two parts, the low frequency ground motion calculated by a numerical method, like FEM, and the high frequency motion synthesized by random approach, and the result of the former is in three dimensional, while that of the latter has just horizontal component. The vertical acceleration time histories proposed in the paper show the way is available.

Trends in Tropospheric Humidity from 1970 to 2008 over China from a Homogenized Radiosonde Dataset

2012 ◽  
Vol 25 (13) ◽  
pp. 4549-4567 ◽  
Author(s):  
Tianbao Zhao ◽  
Aiguo Dai ◽  
Junhong Wang
Keyword(s):  
Spatial Coherence ◽  
Vertical Motion ◽  
Precipitable Water ◽  
Northern China ◽  
Northwest China ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Clapeyron Equation ◽  
Dipole Pattern ◽  
Highly Correlated

Abstract Radiosonde humidity data provide the longest record for assessing changes in atmospheric water vapor, but they often contain large discontinuities because of changes in instrumentation and observational practices. In this study, the variations and trends in tropospheric humidity (up to 300 hPa) over China are analyzed using a newly homogenized radiosonde dataset. It is shown that the homogenization removes the large shifts in the original records of dewpoint depression (DPD) resulting from sonde changes in recent years in China, and it improves the DPD’s correlation with precipitation and the spatial coherence of the DPD trend from 1970 to 2008. The homogenized DPD data, together with homogenized temperature, are used to compute the precipitable water (PW), whose correlation with the PW from ground-based global positioning system (GPS) measurements at three collocated stations is also improved after the homogenization. During 1970–2008 when the record is relatively complete, tropospheric specific humidity after the homogenization shows upward trends, with surface–300-hPa PW increasing by about 2%–5% decade−1 over most of China and by more than 5% decade−1 over northern China in winter. The PW variations and changes are highly correlated with those in lower–midtropospheric mean temperature (r = 0.83), with a dPW/dT slope of ~7.6% K−1, which is slightly higher than the 7% K−1 implied by Clausius–Clapeyron equation with a constant relative humidity (RH). The radiosonde data show only small variations and weak trends in tropospheric RH over China. An empirical orthogonal function (EOF) analysis of the PW reveals several types of variability over China, with the first EOF (31.4% variance) representing an upward PW trend over most of China (mainly since 1987). The second EOF (12.0% variance) shows a dipole pattern between Southeast and Northwest China and it is associated with a similar dipole pattern in atmospheric vertical motion. This mode exhibits mostly multiyear variations that are significantly correlated with Pacific decadal oscillation (PDO) and ENSO indices.

Influence of the vertical motion field on ozone concentration in the stratosphere

1973 ◽  
Vol 106-108 (1) ◽  
pp. 1531-1543 ◽  
Author(s):  
Reginald E. Newell ◽  
George J. Boer ◽  
Thomas G. Dopplick
Keyword(s):  
Ozone Concentration ◽  
Vertical Motion ◽  
Motion Field

Explaining the Spatial Pattern of U.S. Extreme Daily Precipitation Change

2020 ◽  
pp. 1-54
Author(s):  
Martin Hoerling ◽  
Lesley Smith ◽  
Xiao-Wei Quan ◽  
Jon Eischeid ◽  
Joseph Barsugli ◽  
...  
Keyword(s):  
Climate Change ◽  
Daily Precipitation ◽  
Vertical Motion ◽  
Precipitable Water ◽  
Internal Variability ◽  
Atmospheric Model ◽  
Climate Change Signal ◽  
The West ◽  
Appreciable Change ◽  
Trend Pattern

AbstractObserved United States trends in the annual maximum 1-day precipitation (RX1day) over the last century consist of 15% - 25% increases over the East and 10% decreases over the Far West. This heterogeneous trend pattern departs from comparatively uniform observed increases in precipitable water over the contiguous U.S. Here we use an event attribution framework involving parallel sets of global atmospheric model experiments with and without climate change drivers to explain this spatially diverse pattern of extreme daily precipitation trends. We find that RX1day events in our model ensembles respond to observed historical climate change forcing differently across the U.S. with 5%-10% intensity increases over the East but no appreciable change over the West. This spatially diverse forced signal is broadly similar among three models used, and is positively correlated with the observed trend pattern. Our analysis of model and observations indicates the lack of appreciable RX1day signals over the West is likely due to dynamical effects of climate change forcing – via a wintertime atmospheric circulation anomaly that suppresses vertical motion over the West – largely cancelling thermodynamic effects of increased water vapor availability. The large magnitude of eastern U.S. RX1day increases is unlikely a symptom of a regional heightened sensitivity to climate change forcing. Instead, our ensemble simulations reveal considerable variability in RX1day trend magnitudes arising from internal atmospheric processes alone, and we argue that the remarkable observed increases over the East has most likely resulted from a superposition of strong internal variability with a moderate climate change signal. Implications for future changes in U.S. extreme daily precipitation are discussed.

scholarly journals Diagnosing Warm Frontal Cloud Formation in a GCM: A Novel Approach Using Conditional Subsetting

2013 ◽  
Vol 26 (16) ◽  
pp. 5827-5845 ◽  
Author(s):  
James F. Booth ◽  
Catherine M. Naud ◽  
Anthony D. Del Genio
Keyword(s):  
General Circulation ◽  
Vertical Motion ◽  
Circulation Model ◽  
Precipitable Water ◽  
Satellite Observations ◽  
Local Fields ◽  
Cloud Formation ◽  
Initial Structure ◽  
Warm Front ◽  
Low Altitude

Abstract This study analyzes characteristics of clouds and vertical motion across extratropical cyclone warm fronts in the NASA Goddard Institute for Space Studies general circulation model. The validity of the modeled clouds is assessed using a combination of satellite observations from CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), and the NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis. The analysis focuses on developing cyclones, to test the model's ability to generate their initial structure. To begin, the extratropical cyclones and their warm fronts are objectively identified and cyclone-local fields are mapped into a vertical transect centered on the surface warm front. To further isolate specific physics, the cyclones are separated using conditional subsetting based on additional cyclone-local variables, and the differences between the subset means are analyzed. Conditional subsets are created based on 1) the transect clouds and 2) vertical motion; 3) the strength of the temperature gradient along the warm front, as well as the storm-local 4) wind speed and 5) precipitable water (PW). The analysis shows that the model does not generate enough frontal cloud, especially at low altitude. The subsetting results reveal that, compared to the observations, the model exhibits a decoupling between cloud formation at high and low altitudes across warm fronts and a weak sensitivity to moisture. These issues are caused in part by the parameterized convection and assumptions in the stratiform cloud scheme that are valid in the subtropics. On the other hand, the model generates proper covariability of low-altitude vertical motion and cloud at the warm front and a joint dependence of cloudiness on wind and PW.

scholarly journals An objective method for predicting occurrence of pre-monsoon (March-May) thunderstorm events over Delhi using stability indices

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 329-338
Author(s):  
M. DURAISAMY ◽  
S.K.ROY BHOWMIK ◽  
B.K. BANDYOPADHYAY
Keyword(s):  
Free Convection ◽  
Precipitable Water ◽  
Critical Values ◽  
Objective Method ◽  
K Index ◽  
Equilibrium Level ◽  
Stability Indices

In this paper an attempt has been made to investigate different stability indices in relation to the occurrence of thunderstorms in order to determine the critical values of these indices for Delhi (28.35° N / 77.12° E) using pre monsoon data for the years 1999 - 2004. The study shows that the critical values of Showalter Index (SI), Lifted Index (LI), K Index (KI), Total Totals Index (TTI), and Sweat Index (SWI) are respectively < 2 °C, < 0 °C, > 24 °C, > 44.5 °C and > 100 for the thunderstorm to occur over Delhi. The corresponding common critical ranges of Lifted Condensation Level (LCL), Level of Free Convection (LFC), Equilibrium Level (EL) and Precipitable Water (PW) are respectively 923 hPa – 695 hPa, 856 hPa – 504 hPa, 545 hPa – 109 hPa and 18 mm – 54 mm. Testing of critical values of indices and the corresponding common critical ranges of LCL, LFC, EL and PW during pre-monsoon seasons of the years 2005 and 2006 shows that they are matching well with the respective critical values/ranges in most of the thunderstorm days.

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