scholarly journals Summertime Potential Evapotranspiration in Eastern Washington State

2015 ◽  
Vol 54 (5) ◽  
pp. 1090-1101 ◽  
Author(s):  
Nicholas A. Bond ◽  
Karin A. Bumbaco
Keyword(s):  
Relative Humidity ◽  
Pacific Northwest ◽  
Solar Irradiance ◽  
Climate Model ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Global Climate Model ◽  
Washington State ◽  
The Individual ◽  
Eastern Washington

AbstractThe demands for water in agricultural regions depend on the rate of evapotranspiration (ET). Daily records of potential ET (pET) are available from the late 1980s through the present for five stations in eastern Washington State (George, Harrah, LeGrow, Lind, and Odessa) through the Pacific Northwest Cooperative Agricultural Weather Network (AgriMet) under the auspices of the Bureau of Reclamation. These records reveal a secular increase in the summer (June–August) mean pET over the period 1987–2014. This increase can be attributed largely to an increase in solar irradiance of 20–30 W m−2 over the same period. The seasonal mean solar irradiance accounts for approximately 35%–50% of the variance in the interannual variations in seasonal mean pET at the individual stations and for approximately 60% of the variance from a five-station average perspective. The period of analysis includes a mean increase of temperature of about 0.3°C (10 yr)−1, and the variability in temperature relates more to the year-to-year fluctuations in pET than to the overall increase in pET. The time series of surface relative humidity and wind speed exhibit only minor trends. Daily and seasonal mean data for 500-hPa geopotential height and other variables are used to determine aspects of the regional atmosphere associated with periods of high pET. Anomalous ridging aloft and negative anomalies in 925-hPa relative humidity tend to occur over the study area during the summers with the greatest pET. The relationships that are emerging may provide a basis for empirical downscaling of pET from global climate model projections.

scholarly journals Role of the Convection Scheme in Modeling Initiation and Intensification of Tropical Depressions over the North Atlantic

2017 ◽  
Vol 145 (4) ◽  
pp. 1495-1509 ◽  
Author(s):  
J.-P. Duvel ◽  
S. J. Camargo ◽  
A. H. Sobel
Keyword(s):  
Relative Humidity ◽  
Climate Model ◽  
Early Stage ◽  
Global Climate ◽  
Global Climate Model ◽  
Convective Available Potential Energy ◽  
Convective Precipitation ◽  
Cloud Base ◽  
Entrainment Rate ◽  
Convection Scheme

Abstract The authors analyze how modifications of the convective scheme modify the initiation of tropical depression vortices (TDVs) and their intensification into stronger warm-cored tropical cyclone–like vortices (TCs) in global climate model (GCM) simulations. The model’s original convection scheme has entrainment and cloud-base mass flux closures based on moisture convergence. Two modifications are considered: one in which entrainment is dependent on relative humidity and another in which the closure is based on the convective available potential energy (CAPE). Compared to reanalysis, TDVs are more numerous and intense in all three simulations, probably as a result of excessive parameterized deep convection at the expense of convection detraining at midlevel. The relative humidity–dependent entrainment rate increases both TDV initiation and intensification relative to the control. This is because this entrainment rate is reduced in the moist center of the TDVs, giving more intense convective precipitation, and also because it generates a moister environment that may favor the development of early stage TDVs. The CAPE closure inhibits the parameterized convection in strong TDVs, thus limiting their development despite a slight increase in the resolved convection. However, the maximum intensity reached by TC-like TDVs is similar in the three simulations, showing the statistical character of these tendencies. The simulated TCs develop from TDVs with different dynamical origins than those observed. For instance, too many TDVs and TCs initiate near or over southern West Africa in the GCM, collocated with the maximum in easterly wave activity, whose characteristics are also dependent on the convection scheme considered.

scholarly journals The role of atmosphere and ocean physical processes in ENSO in a perturbed physics coupled climate model

Ocean Science ◽  
2010 ◽  
Vol 6 (2) ◽  
pp. 441-459 ◽  
Author(s):  
S. Y. Philip ◽  
M. Collins ◽  
G. J. van Oldenborgh ◽  
B. J. J. M. van den Hurk
Keyword(s):  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Minor Role ◽  
Wind Variability ◽  
Sst Variability ◽  
Climate Model Simulations ◽  
The Individual ◽  
Perturbed Physics

Abstract. We examine the behaviour of the El Niño – Southern Oscillation (ENSO) in an ensemble of global climate model simulations with perturbations to parameters in the atmosphere and ocean components respectively. The influence of the uncertainty in these parametrisations on ENSO are investigated systematically. The ensemble exhibits a range of different ENSO behaviour in terms of the amplitude and spatial structure of the sea surface temperature (SST) variability. The nature of the individual feedbacks that operate within the ENSO system are diagnosed using an Intermediate Complexity Model (ICM), which has been used previously to examine the diverse ENSO behaviour of the CMIP3 multi-model ensemble. Unlike in that case, the ENSO in these perturbed physics experiments is not principally controlled by variations in the mean climate state. Rather the parameter perturbations influence the ENSO characteristics by modifying the coupling feedbacks within the cycle. The associated feedbacks that contribute most to the ensemble variations are the response of SST to local wind variability and damping, followed by the response of SST to thermocline anomalies and the response of the zonal wind stress to those SST anomalies. Atmospheric noise amplitudes and oceanic processes play a relatively minor role.

Estimates of Twenty-First-Century Flood Risk in the Pacific Northwest Based on Regional Climate Model Simulations

2014 ◽  
Vol 15 (5) ◽  
pp. 1881-1899 ◽  
Author(s):  
Eric P. Salathé ◽  
Alan F. Hamlet ◽  
Clifford F. Mass ◽  
Se-Yeun Lee ◽  
Matt Stumbaugh ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Statistical Downscaling ◽  
Flood Risk ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Climate ◽  
Hydrologic Model ◽  
The Pacific ◽  
Physically Based

Abstract Results from a regional climate model simulation show substantial increases in future flood risk (2040–69) in many Pacific Northwest river basins in the early fall. Two primary causes are identified: 1) more extreme and earlier storms and 2) warming temperatures that shift precipitation from snow to rain dominance over regional terrain. The simulations also show a wide range of uncertainty among different basins stemming from localized storm characteristics. While previous research using statistical downscaling suggests that many areas in the Pacific Northwest are likely to experience substantial increases in flooding in response to global climate change, these initial estimates do not adequately represent the effects of changes in heavy precipitation. Unlike statistical downscaling techniques applied to global climate model scenarios, the regional model provides an explicit, physically based simulation of the seasonality, size, location, and intensity of historical and future extreme storms, including atmospheric rivers. This paper presents climate projections from the ECHAM5/Max Planck Institute Ocean Model (MPI-OM) global climate model dynamically downscaled using the Weather Research and Forecasting (WRF) Model implemented at 12-km resolution for the period 1970–2069. The resulting daily precipitation and temperature data are bias corrected and used as input to a physically based Variable Infiltration Capacity (VIC) hydrologic model. From the daily time step simulations of streamflow produced by the hydrologic model, probability distributions are fit to the extreme events extracted from each water year and flood statistics for various return intervals are estimated.

scholarly journals A single column simulation-based decomposition of the tropical upper tropospheric warming

2021 ◽  
pp. 1-36
Author(s):  
Yuwei Wang ◽  
Yi Huang
Keyword(s):  
Relative Humidity ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Dilution Effect ◽  
Lapse Rate ◽  
Modeling Framework ◽  
Single Column ◽  
Convective Adjustment

AbstractAn atmospheric global climate model (GCM) and its associated single-column model are used to study the tropical upper tropospheric warming and elucidate how different processes drive this warming. In this modeling framework, on average the direct radiative process accounts for 13% of the total warming. The radiation increases the atmospheric lapse rate and triggers more convection, which further produces 74% of the total warming. The rest 13% is attributable to the circulation adjustment. The relative importance of these processes differs in different regions. In the deep tropics, the radiative-convective adjustment produces the most significant warming and accounts for almost 100% of the total warming. In the subtropics, the radiative-convective adjustment accounts for 73% of the total warming and the circulation adjustment plays a more important role than in the deep tropics, especially at the levels above 200 hPa. When the lateral boundary conditions, i.e. the temperature and water vapor advections, are held fixed in single-column simulations, the tropospheric relative humidity significantly increases in the radiative-convective adjustment in response to the surface warming. This result, in contrast to the relative humidity conservation behavior in the GCM, highlights the importance of circulation adjustment in maintaining the constant relative humidity. The tropical upper tropospheric warming in both the full GCM and the single-column simulations is found to be less strong than the warming predicted by reference moist adiabats. This evidences that the sub-moist-adiabat warming occurs even without the dilution effect of the large-scale circulation adjustment.

scholarly journals The role of atmosphere and ocean physical processes in ENSO

2009 ◽  
Vol 6 (3) ◽  
pp. 2037-2083 ◽  
Author(s):  
S. Y. Philip ◽  
M. Collins ◽  
G. J. van Oldenborgh ◽  
B. J. J. M. van den Hurk
Keyword(s):  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Minor Role ◽  
Wind Variability ◽  
Sst Variability ◽  
Parameter Perturbations ◽  
Climate Model Simulations ◽  
The Individual

Abstract. We examine the behaviour of the El Niño – Southern Oscillation (ENSO) in an ensemble of global climate model simulations with perturbations to parameters in the atmosphere and ocean components respectively. The influence of the uncertainty in these parametrisations on ENSO are investigated systematically. The ensemble exhibits a range of different ENSO behaviour in terms of the amplitude and spatial structure of the SST variability. The nature of the individual feedbacks that operate within the ENSO system are diagnosed using an Intermediate Complexity Model (ICM), which has been used previously to examine the diverse ENSO behaviour of the CMIP3 multi-model ensemble. Unlike in that case, the ENSO in these perturbed physics experiments is not principally controlled by variations in the mean climate state. Rather the parameter perturbations influence the ENSO characteristics by modifying the coupling feedbacks within the cycle. The associated feedbacks that contribute most to the ensemble variations are the response of SST to local wind variability and damping, followed by the response of SST to thermocline anomalies and the response of the zonal wind stress to those SST anomalies. Atmospheric noise amplitudes and oceanic processes play a relatively minor role.

Diagnosis of Zonal Mean Relative Humidity Changes in a Warmer Climate

2010 ◽  
Vol 23 (17) ◽  
pp. 4556-4569 ◽  
Author(s):  
Jonathon S. Wright ◽  
Adam Sobel ◽  
Joseph Galewsky
Keyword(s):  
Relative Humidity ◽  
Climate Model ◽  
Transport Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Lower Troposphere ◽  
Hadley Cell ◽  
Tracer Transport ◽  
Transport Pathways ◽  
Extratropical Tropopause

Abstract The zonal mean relative humidity response to a doubling of CO2 in a climate model is examined using a global climate model and an offline tracer transport model. Offline tracer transport model simulations are driven by the output from two configurations of the climate model, one with 1979 concentrations of atmospheric greenhouse gases and one with doubled CO2. A set of last saturation tracers is applied within the tracer transport model to diagnose the dynamics responsible for features in the water vapor field. Two different methods are used to differentiate the effects of circulation and transport shifts from spatially inhomogeneous temperature changes. The first of these uses the tracer transport model and is achieved by decoupling the input temperature and circulation fields; the second uses the reconstruction of humidity from the last saturation tracers and is achieved by decoupling the tracer concentrations from their saturation specific humidities. The responses of the tropical and subtropical relative humidities are found to be largely dependent on circulation and transport changes, particularly a poleward expansion of the Hadley cell, a deepening of the height of convective detrainment, a poleward shift of the extratropical jets, and an increase in the height of the tropopause. The last saturation tracers are used to illustrate the influence of changes in transport pathways within the GCM on the zonal mean relative humidity, particularly in the tropical upper troposphere and subtropical dry zones. Relative humidity changes near the extratropical tropopause and in the lower troposphere are largely dependent on changes in the distribution and gradients of temperature. Increases in relative humidity near the extratropical tropopause in both hemispheres are coincident with increases in the occurrence of local saturation and high cloud cover.

scholarly journals Analysis of climate change effects on evapotranspiration in the watershed Uhlířská in the Jizera Mountains

2010 ◽  
Vol 5 (No. 1) ◽  
pp. 28-38 ◽  
Author(s):  
M. Remrová ◽  
M. Císlerová
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Water Movement ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Climate ◽  
Climatic Conditions ◽  
Weather Data ◽  
Atmospheric Conditions

This study has been conducted with the aim to analyse the hydrology balance in the experimental watershed Uhlířská under the actual atmospheric conditions and expected climate changes in the upcoming years. The main accent is put on the water availability for the water root uptake by the dominant grass vegetation (Calamagrostis villosa). Special attention is paid to the seasonal potential evapotranspiration estimation under mountain climatic conditions. Three methods for the potential evapotranspiration quantification are analysed in order to find out the most acceptable approach for future periods for which no adequate weather data are available. The future precipitation and temperature data are simulated by the regional climate model HIRHAM which is driven by global climate model HadCM3. The data are simulated for the period from 2071 to 2100. The modelling of the soil water movement (using S1D model) is carried out on selected 18 years from the period of 1961–2005 and on selected 10 climate-change-affected years with extremely low precipitations high temperatures. The results of the scenario presented do not indicate that the climatic changes should significantly affect the hydrological balance in the studied area in terms of evapotranspiration up to the year 2100. Due to the lower seasonal precipitation and higher air the temperature, was increased in the results of simulations under the defined approach, however, the local vegetation cover did not suffer from insufficient water supply. These considerations are close to the simulation models used.

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

1996 ◽  
Author(s):  
Larry Bergman ◽  
J. Gary ◽  
Burt Edelson ◽  
Neil Helm ◽  
Judith Cohen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Bit Rate ◽  
Global Science ◽  
High Bit Rate

scholarly journals A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

2010 ◽  
Vol 10 (14) ◽  
pp. 6527-6536 ◽  
Author(s):  
M. A. Brunke ◽  
S. P. de Szoeke ◽  
P. Zuidema ◽  
X. Zeng
Keyword(s):  
Diurnal Cycle ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Southeast Pacific ◽  
Cloud Thickness

Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003–2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

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