scholarly journals The Role of Sea Surface Temperature in Reanalysis

2006 ◽  
Vol 134 (2) ◽  
pp. 532-552 ◽  
Author(s):  
Masao Kanamitsu ◽  
Seung-On Hwang
Keyword(s):  
Surface Temperature ◽  
Surface Pressure ◽  
Low Frequency ◽  
Radiosonde Data ◽  
Observation System ◽  
Control Analysis ◽  
Near Surface ◽  
Upper Level ◽  
The Impact

Abstract With the aim of understanding the role of SST in the reanalysis for the preradiosonde, presatellite, and satellite eras, a number of observation system experiments were performed using the NCEP/Department of Energy (DOE) reanalysis system. Five pairs of experiments were conducted using observed and climatological SSTs for cases 1) without any observation, 2) surface pressure observation only with the observation density of 1915, 3) surface pressure observation with the observation density of 1997, 4) surface observation and radiosondes, and 5) all observations, including satellite retrievals. The analyses were run for 4 months in 1997 (strong El Niño) and 1993 (near-normal SST). The impact of SST and the various observation systems on the analysis of near-surface parameters, the upper-level field, and several diagnostic fields were compared against the control analysis with observed SST and all available observations. The most important finding of this study is that the impact of SST varies with the time scale of the analysis, which is most apparent in the surface-pressure-only observation experiments. The impact of SST is largest for the low-frequency (seasonal) analyses and smaller for the high-frequency (daily) analyses. This is particularly apparent for near-surface temperature and upper-level height field analyses. In the extreme case of the strong El Niño year, the simulation with observed SST without any observations [Atmospheric Model Intercomparison Project (AMIP)-type run] produced seasonal mean 2-m temperature (T2M) and 500-hPa height fields that agreed better with the control analysis than the analysis with surface pressure observation only with climatological SST. On the contrary, the impact of surface pressure observation is greater on higher-frequency analyses, and lower on low-frequency analyses. Generally speaking, accurate analysis of SST is important when limited atmospheric observation is available. But even for the full atmospheric observation system, climatological SST produces inferior analysis over ocean as well as land. The introduction of radiosonde data drastically reduces errors in the analyses and diagnostic fields; thus, radiosonde data are indispensable for accurate estimation of the atmospheric state in both short and long time scales.

Evaluating the role of soil physical properties on simulated land-atmosphere interactions over South Africa using coupled atmosphere-hydrological modeling

2021 ◽  
Author(s):  
Zhenyu Zhang ◽  
Patrick Laux ◽  
Joël Arnault ◽  
Jianhui Wei ◽  
Jussi Baade ◽  
...  
Keyword(s):  
South Africa ◽  
Physical Properties ◽  
Land Degradation ◽  
Land Surface ◽  
Soil Physical Properties ◽  
Near Surface ◽  
Soil Database ◽  
Global Soil ◽  
The Impact

<p>Land degradation with its direct impact on vegetation, surface soil layers and land surface albedo, has great relevance with the climate system. Assessing the climatic and ecological effects induced by land degradation requires a precise understanding of the interaction between the land surface and atmosphere. In coupled land-atmosphere modeling, the low boundary conditions impact the thermal and hydraulic exchanges at the land surface, therefore regulates the overlying atmosphere by land-atmosphere feedback processes. However, those land-atmosphere interactions are not convincingly represented in coupled land-atmosphere modeling applications. It is partly due to an approximate representation of hydrological processes in land surface modeling. Another source of uncertainties relates to the generalization of soil physical properties in the modeling system. This study focuses on the role of the prescribed physical properties of soil in high-resolution land surface-atmosphere simulations over South Africa. The model used here is the hydrologically-enhanced Weather Research and Forecasting (WRF-Hydro) model. Four commonly used global soil datasets obtained from UN Food and Agriculture Organization (FAO) soil database, Harmonized World Soil Database (HWSD), Global Soil Dataset for Earth System Model (GSDE), and SoilGrids dataset, are incorporated within the WRF-Hydro experiments for investigating the impact of soil information on land-atmosphere interactions. The simulation results of near-surface temperature, skin temperature, and surface energy fluxes are presented and compared to observational-based reference dataset. It is found that simulated soil moisture is largely influenced by soil texture features, which affects its feedback to the atmosphere.</p>

NMME-based Assessment of Prediction Skills of US Summertime Droughts and Pluvials: Role of Near-surface Temperature Prediction Skill

2021 ◽  
Author(s):  
Jonghun Kam ◽  
Sungyoon Kim ◽  
Joshua Roundy
Keyword(s):  
Surface Temperature ◽  
Climate Extremes ◽  
Prediction Skill ◽  
Seasonal Forecasts ◽  
Near Surface ◽  
Anomaly Correlation ◽  
The North ◽  
Anomaly Correlation Coefficient ◽  
Precipitation Anomalies

<p>This study used the North American Multi-Model Ensemble (NMME) system to understand the role of near surface temperature in the prediction skill for US climate extremes. In this study, the forecasting skill was measured by anomaly correlation coefficient (ACC) between the observed and forecasted precipitation (PREC) or 2-meter air temperature (T2m) over the contiguous United States (CONUS) during 1982–2012. The strength of the PREC-T2m coupling was measured by ACC between observed PREC and T2m or forecasted PREC and T2m over the CONUS. This study also assessed the NMME forecasting skill for the summers of 2004 (spatial anomaly correlation between PREC and T2m: 0.05), 2011 (-0.65), and 2012 (-0.60) when the PREC-T2m coupling is weaker or stronger than the 1982–2012 climatology (ACC:-0.34). This study found that most of the NMME models show stronger (negative) PREC-T2m coupling than the observed coupling, indicating that they fail to reproduce interannual variability of the observed PREC-T2m coupling. Some NMME models with skillful prediction for T2m show the skillful prediction of the precipitation anomalies and US droughts in 2011 and 2012 via strong PREC-T2m coupling despite the fact that the forecasting skill is year-dependent and model-dependent. Lastly, we explored how the forecasting skill for SSTs over north Pacific and Atlantic Oceans affects the forecasting skill for T2m and PREC over the US. The findings of this study suggest a need for the selective use of the current NMME seasonal forecasts for US droughts and pluvials.</p>

scholarly journals Southeastern Australian Heat Waves from a Trajectory Viewpoint

2017 ◽  
Vol 145 (10) ◽  
pp. 4109-4125 ◽  
Author(s):  
Julian F. Quinting ◽  
Michael J. Reeder
Keyword(s):  
Indian Ocean ◽  
Heat Wave ◽  
Heat Waves ◽  
The South ◽  
South Indian Ocean ◽  
Near Surface ◽  
South Indian ◽  
Eastern Australia ◽  
Upper Level

Although heat waves account for more premature deaths in the Australian region than any other natural disaster, an understanding of their dynamics is still incomplete. The present study identifies the dynamical mechanisms responsible for heat waves in southeastern Australia using 10-day backward trajectories computed from the ERA-Interim reanalyses. Prior to the formation of a heat wave, trajectories located over the south Indian Ocean and over Australia in the lower and midtroposphere ascend diabatically ahead of an upper-level trough and over a baroclinic zone to the south of the continent. These trajectories account for 44% of all trajectories forming the anticyclonic upper-level potential vorticity anomalies that characterize heat waves in the region. At the same time, trajectories located over the south Indian Ocean in the lower part of the troposphere descend and aggregate over the Tasman Sea. This descent is accompanied by a strong adiabatic warming. A key finding is that the temperatures are raised further through diabatic heating in the boundary layer over eastern Australia but not over the inner Australian continent. From eastern Australia, the air parcels are advected southward as they become incorporated into the near-surface anticyclone that defines the heat wave. In contrast to past studies, the importance of cloud-diabatic processes in the evolution of the midlatitude large-scale flow and the role of adiabatic compression in elevating the near-surface temperatures is emphasized. Likewise, the role of the local surface sensible heat fluxes is deemphasized.

scholarly journals High-Resolution, Rapid-Scan Dual-Doppler Retrievals of Vertical Velocity in a Simulated Supercell

2019 ◽  
Vol 36 (8) ◽  
pp. 1477-1500 ◽  
Author(s):  
Nathan A. Dahl ◽  
Alan Shapiro ◽  
Corey K. Potvin ◽  
Adam Theisen ◽  
Joshua G. Gebauer ◽  
...  
Keyword(s):  
Variational Method ◽  
Vertical Velocity ◽  
Traditional Method ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Observation System ◽  
Near Surface ◽  
Rapid Scan ◽  
Close Range ◽  
The Impact

AbstractObservation system simulation experiments are used to evaluate different dual-Doppler analysis (DDA) methods for retrieving vertical velocity w at grid spacings on the order of 100 m within a simulated tornadic supercell. Variational approaches with and without a vertical vorticity equation constraint are tested, along with a typical (traditional) method involving vertical integration of the mass conservation equation. The analyses employ emulated radar data from dual-Doppler placements 15, 30, and 45 km east of the mesocyclone, with volume scan intervals ranging from 10 to 150 s. The effect of near-surface data loss is examined by denying observations below 1 km in some of the analyses. At the longer radar ranges and when no data denial is imposed, the “traditional” method produces results similar to those of the variational method and is much less expensive to implement. However, at close range and/or with data denial, the variational method is much more accurate, confirming results from previous studies. The vorticity constraint shows the potential to improve the variational analysis substantially, reducing errors in the w retrieval by up to 30% for rapid-scan observations (≤30 s) at close range when the local vorticity tendency is estimated using spatially variable advection correction. However, the vorticity constraint also degrades the analysis for longer scan intervals, and the impact diminishes with increased range. Furthermore, analyses using 30-s data also frequently outperform analyses using 10-s data, suggesting a limit to the benefit of increasing the radar scan rate for variational DDA employing the vorticity constraint.

scholarly journals Response of Near-Surface Meteorological Conditions to Advection under Impact of the Green Roof

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 759
Author(s):  
Haochen Tan ◽  
Pallav Ray ◽  
Mukul Tewari ◽  
James Brownlee ◽  
Ajaya Ravindran
Keyword(s):  
Surface Temperature ◽  
Urban Areas ◽  
Green Roof ◽  
Wrf Model ◽  
Single Layer ◽  
Meteorological Conditions ◽  
Rapid Urbanization ◽  
Near Surface ◽  
Budget Analysis ◽  
The Impact

Due to rapid urbanization, the near-surface meteorological conditions over urban areas are greatly modulated. To capture such modulations, sophisticated urban parameterizations with enhanced hydrological processes have been developed. In this study, we use the single-layer urban canopy model (SLUCM) available within the Weather Research and Forecasting (WRF) model to assess the response of near-surface temperature, wind, and moisture to advection under the impact of the green roof. An ensemble of simulations with different planetary boundary layer (PBL) schemes is conducted in the presence (green roof (GR)) and absence (control (CTL)) of green roof systems. Our results indicate that the near-surface temperature is found to be driven primarily by the surface heat flux with a minor influence from the zonal advection of temperature. The momentum budget analysis shows that both zonal and meridional momentum advection during the evening and early nighttime plays an important role in modulating winds over urban areas. The near-surface humidity remains nearly unchanged in GR compared to CTL, although the physical processes that determine the changes in humidity were different, in particular during the evening when the GR tends to have less moisture advection due to the reduced temperature gradient between the urban areas and the surroundings. Implications of our results are discussed.

Role of Advection on the Evolution of Near-Surface Temperature and Wind in Urban-Aware Simulations

2020 ◽  
Author(s):  
Pallav Ray ◽  
Haochen Tan ◽  
Mukul Tewari ◽  
James Brownlee ◽  
R. S. Ajayamohan ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Urban Areas ◽  
Single Layer ◽  
Windward Side ◽  
Leeward Side ◽  
Land Use Patterns ◽  
Near Surface ◽  
Horizontal Advection ◽  
The City

AbstractThe role of advection of heat and momentum on the evolution of near-surface temperature and wind is evaluated in urban-aware simulations over Houston under dry conditions on a light-wind day. Two sets of experiments, each consisting of four simulations using different planetary boundary layer (PBL) schemes, were conducted over 48 hours using the default urban scheme (BULK) and the single-layer urban canopy model (SLUCM) available within the Weather Research and Forecasting (WRF) model. We focus on understanding and quantifying the role played by temperature and momentum advection, particularly on the windward and leeward sides of the city. Previous studies have largely ignored any quantitative analysis of impacts from the advection of momentum over an urban area.The horizontal advection of temperature was found to be more important in the BULK because of the larger surface temperature gradient caused by warmer surface temperatures over urban areas than in the SLUCM. An analysis of the momentum budget shows that horizontal advection of zonal and meridional momentum plays a prominent role during the period of peak near-surface winds, and this effect is more pronounced in the windward side of the city. The local tendency in peak winds in the leeward side lags that in the windward side by about 1-2 hours, similar to the lag found in horizontal momentum advection. The sensitivity of the results to different urban and PBL schemes was explored. The results imply that representation and influence of land-use patterns via sophisticated urban parameterizations generates locally driven winds that best resemble observations.

scholarly journals Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change

2006 ◽  
Vol 19 (12) ◽  
pp. 2763-2782 ◽  
Author(s):  
Peter A. Stott ◽  
Gareth S. Jones ◽  
Jason A. Lowe ◽  
Peter Thorne ◽  
Chris Durman ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Temperature ◽  
Land Use Changes ◽  
First Century ◽  
Radiosonde Data ◽  
Anthropogenic Influence ◽  
Near Surface ◽  
Temperature Changes ◽  
Hadley Centre ◽  
Anthropogenic Forcings

Abstract The ability of climate models to simulate large-scale temperature changes during the twentieth century when they include both anthropogenic and natural forcings and their inability to account for warming over the last 50 yr when they exclude increasing greenhouse gas concentrations has been used as evidence for an anthropogenic influence on global warming. One criticism of the models used in many of these studies is that they exclude some forcings of potential importance, notably from fossil fuel black carbon, biomass smoke, and land use changes. Herein transient simulations with a new model, the Hadley Centre Global Environmental Model version 1 (HadGEM1), are described, which include these forcings in addition to other anthropogenic and natural forcings, and a fully interactive treatment of atmospheric sulfur and its effects on clouds. These new simulations support previous work by showing that there was a significant anthropogenic influence on near-surface temperature change over the last century. They demonstrate that black carbon and land use changes are relatively unimportant for explaining global mean near-surface temperature changes. The pattern of warming in the troposphere and cooling in the stratosphere that has been observed in radiosonde data since 1958 can only be reproduced when the model includes anthropogenic forcings. However, there are some discrepancies between the model simulations and radiosonde data, which are largest where observational uncertainty is greatest in the Tropics and high latitudes. Predictions of future warming have also been made using the new model. Twenty-first-century warming rates, following policy-relevant emissions scenarios, are slightly greater in HadGEM1 than in the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) as a result of the extra forcing in HadGEM1. An experiment in which greenhouse gases and other anthropogenic forcings are stabilized at 2100 levels and held constant until 2200 predicts a committed twenty-second-century warming of less than 1 K, whose spatial distribution resembles that of warming during the twenty-first century, implying that the local feedbacks that determine the pattern of warming do not change significantly.

Experimental Study on the Role of Entropy Waves in Low-Frequency Oscillations for a Diffusion Burner

2004 ◽  
Author(s):  
J. Eckstein ◽  
E. Freitag ◽  
C. Hirsch ◽  
T. Sattelmayer
Keyword(s):  
Experimental Study ◽  
Low Frequency ◽  
Feedback Mechanism ◽  
Mean Flow ◽  
Primary Zone ◽  
Start Up ◽  
Atomization Characteristics ◽  
Aero Engines ◽  
The Impact

“Rumble” is a self-excited combustion instability, usually occurring at the start-up of aero-engines with fuel-spray atomizers at sub-idle and idle conditions, and exhibiting low limit frequencies in the range of 50 Hz to 150 Hz. Entropy waves at the (nearly) choked combustor outlet are supposed to be the key feedback-mechanism for the observed self-excited pressure oscillations. The experimental study presented here aims to clarify the role of the entropy waves for the occurrence of rumble. A generic air-blast atomizer with a design being prone to self-excitation has been incorporated into a thermoacoustic combustor test rig with variable outlet conditions. The flame thermoacoustics were characterized by recording the OH*-chemiluminescence, the dynamic pressures, the dynamic temperatures, and by applying PIV. The measurements have shown the occurrence of periodic hot spots travelling with the mean flow with considerable dispersion. Measurements have been conducted with an open-ended resonance tube in order to eliminate the impact of entropy waves on the mechanism of self-excitation. The oscillation obtained, comparable in amplitude and frequency, proved that self-excitation primarily depends on convective time delays of the droplets in the primary zone and thus on the atomization characteristics of the nozzle.

scholarly journals The Diurnal Cycle of Land–Atmosphere Interactions across Oklahoma’s Winter Wheat Belt

2005 ◽  
Vol 133 (1) ◽  
pp. 120-130 ◽  
Author(s):  
Matthew J. Haugland ◽  
Kenneth C. Crawford
Keyword(s):  
Soil Moisture ◽  
Winter Wheat ◽  
Surface Pressure ◽  
Diurnal Cycle ◽  
Wheat Crop ◽  
Near Surface ◽  
Diurnal Cycles ◽  
Dewpoint Temperature ◽  
Before And After ◽  
The Impact

Abstract This manuscript documents the impact of Oklahoma’s winter wheat belt (WWB) on the near-surface atmosphere by comparing the diurnal cycle of meteorological conditions within the WWB relative to conditions in adjacent counties before and after the wheat harvest. To isolate the impact of the winter wheat belt on the atmosphere, data from several meteorological parameters were averaged to create a diurnal cycle before and after the wheat harvest. Observations from 17 Oklahoma Mesonet sites within the WWB (during a period of 9 yr) were compared with observations from 22 Mesonet sites in adjacent counties outside the winter wheat belt. The average diurnal cycles of dewpoint, temperature, and surface pressure exhibited patterns that revealed a distinct mesoscale impact of the wheat fields. The diurnal patterns were consistent with the status of the wheat crop and the grassland in adjacent counties. The impact of the WWB was shown to be more significant during a month when soil moisture was abundant, and minimal during a month when soil moisture was limited. Statistically significant, hydrostatically consistent afternoon surface pressure anomalies suggest that there is a strong possibility of weak mesoscale circulations induced by the WWB.

scholarly journals Administrative corruption in the static model of balancing common and private interests

2021 ◽  
pp. 9-19
Author(s):  
Olga Ivanovna Gorbaneva
Keyword(s):  
Level Sets ◽  
Lower Boundary ◽  
Static Model ◽  
Optimization Approach ◽  
Level System ◽  
Private Interests ◽  
Descriptive Approach ◽  
Upper Level ◽  
The Impact

  This article is dedicated to examination of corruption in the previously researched static model of balancing common and private interests (SOCHI-models). In the previously considered two-level system, between the upper non-corrupted level and the lower – agents, is introduced the average level which in exchange for a bribe, can weaken the influence of the upper level. The upper level sets the minimum amount of resources for an agent to spend on general purposes. A supervisor, in exchange for a bribe, the role of which is played by the share of agent’s private income, can reduce this lower boundary, allowing the latter to spend more resources on private purposes. This article reviews the three-level hierarchical system “Principal-Supervisor-Agents”, where the supervisor uses the administrative corruption mechanism, which requires two descriptive and optimization approaches towards its examination. The descriptive approach suggests that the considered functions of bribery are known; while the optimization approach implies the use of Germeyer’s theorem. The author explores the impact of administrative corruption upon systemic congruence of the SOCHI-model: it is proven that the administrative corruption can only reduce congruence. The author finds the conditions that can beat or reduce administrative corruption can, as well as conditions when corruption is disadvantageous for supervisor or agent. The article determines the circle of agents that supervisor can exert influence upon.  

Sign in / Sign up

Export Citation Format

Share Document