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The Precipitation Response to an Idealized Subtropical Continent

JOURNAL OF CLIMATE 2016年第12期29卷 4543-4564页

作者： Maroon, Elizabeth A. Frierson, Dargan M. W. Kang, Sarah M. Scheff, Jacob Univ Washington Dept Atmospher Sci Box 351640 Seattle WA 98115 USA Ulsan Natl Inst Sci & Technol Sch Urban & Environm Engn Ulsan South Korea Columbia Univ Lamont Doherty Earth Observ Palisades NY USA

A subtropical continent is added to two aquaplanet atmospheric general circulation models (AGCMs) to better understand the influence of land on tropical circulation and precipitation. The first model, the gray-radiation moist (GRaM) AGCM, has simplified physics, while the second model, the GFDL Atmospheric Model version 2.1 (AM2.1), is a fully comprehensive AGCM. Both models have a continent that is 608 wide in longitude from 10 degrees to 30 degrees N, in an otherwise slab-ocean-covered world. The precipitation response varies with cloudy-and clear-sky feedbacks and depends on continental albedo. In GRaM simulations with a continent, precipitation in the Northern Hemisphere decreases mostly as a result of decreased evaporation. In AM2.1 simulations, precipitation also shifts southward via Hadley circulation changes due to increasing albedo, but the radiative impact of clouds and moisture creates a more complex response. Results are similar when a seasonal cycle of insolation is included in AM2.1 simulations. The impact of a large, bright subtropical continent is to shift precipitation to the opposite hemisphere. In these simulations, the hemisphere of greater tropical precipitation is better predicted by the hemisphere with greater atmospheric energy input, as has been shown in previous literature, rather than the hemisphere that has higher surface temperature.

关键词： Geographic location/entity Intertropical convergence zone Circulation/ Dynamics Energy transport Hadley circulation Atm/Ocean Structure/ Phenomena Monsoons Precipitation models and modeling General circulation models

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Quantifying the Incoherent M₂ Internal Tide in the Philippine Sea

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JOURNAL OF PHYSICAL OCEANOGRAPHY 2016年第8期46卷 2483-2491页

作者： Kerry, Colette G. Powell, Brian S. Carter, Glenn S. Univ Hawaii Manoa Honolulu HI 96822 USA Univ New South Wales Sydney NSW Australia

The baroclinic tides are a crucial source of mixing energy into the deep ocean;however, the incoherent portion of the spectrum is not well examined because it is difficult to observe. This study estimates the coherent and incoherent M-2 internal tide energy fluxes in the Philippine Sea using a primitive equation model that resolves the M-2 barotropic and baroclinic tides and the time-evolving atmospherically forced eddying circulation. A time-mean, incoherent, internal tide energy flux of 25% of the coherent energy flux is found to emanate eastward into the Philippine Sea from the Luzon Strait and a time-mean incoherent portion of 30% of the coherent energy flux propagates westward into the South China Sea (SCS). The incoherent internal tide energy results from baroclinic tide generation and propagation variability. Quantifying the incoherent portion estimates the energy missing from altimeter-derived or line-integral acoustic measurements and places short-lived, in situ observations in the context of variability.

关键词： Geographic location/entity North Pacific Ocean Circulation/ Dynamics Internal waves Atm/Ocean Structure/ Phenomena Tides models and modeling Ocean models Variability Oceanic variability

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Improvements in Land-Use Classification for Estimating Daytime Surface Temperatures and Sea-Breeze Flows in Southern California

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EARTH INTERACTIONS 2016年第16期20卷 1-32页

作者： Sequera, Pedro Gonzalez, Jorge E. McDonald, Kyle LaDochy, Steve Comarazamy, Daniel CUNY City Coll Dept Mech Engn 140th St & Convent AveSteinman HallRoom T-238 New York NY 10031 USA CUNY City Coll Dept Earth & Atmospher Sci New York NY 10031 USA Calif State Univ Los Angeles Dept Geosci & Environm Los Angeles CA 90032 USA CUNY City Coll NOAA CREST Ctr New York NY 10031 USA

Understanding the interactions between large-scale atmospheric and oceanic circulation patterns and changes in land cover and land use (LCLU) due to urbanization is a relevant subject in many coastal climates. Recent studies by Lebassi et al. found that the average maximum air temperatures during the summer in two populated California coastal areas decreased at low-elevation areas open to marine air penetration during the period of 1970-2005. This coastal cooling was attributed to an increase in sea-breeze activity. The aims of this work are to better understand the coastal flow patterns and sea-land thermal gradient by improving the land-cover classification scheme in the region using updated airborne remote sensing data and to assess the suitability of the updated regional atmospheric modeling system for representing maritime flows in this region. This study uses high-resolution airborne data from the NASA Hyperspectral Infrared Imager (HyspIRI) mission preparatory flight campaign over Southern California and surface ground stations to compare observations against model estimations. Five new urban land classes were created using broadband albedo derived from the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) sensor and then assimilated into the Weather Research and Forecasting (WRF) Model. The updated model captures the diurnal spatial and temporal sea-breeze patterns in the region. Results show notable improvements of simulated daytime surface temperature and coastal winds using the HyspIRI-derived products in the model against the default land classification, reaffirming the importance of accounting for heterogeneity of urban surface properties.

关键词： Circulation/dynamics Atmosphere-land interaction Atmosphere/ocean structure/phenomena Sea breezes Observational techniques and algorithms Remote sensing Mathematical and statistical techniques Classification models and modeling Mesoscale models Applications Land use

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The POWER Experiment: Impact of Assimilation of a Network of Coastal Wind Profiling Radars on Simulating Offshore Winds in and above the Wind Turbine Layer

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WEATHER AND FORECASTING 2016年第4期31卷 1071-1091页

作者： Djalalova, Irina V. Olson, Joseph Carley, Jacob R. Bianco, Laura Wilczak, James M. Pichugina, Yelena Banta, Robert Marquis, Melinda Cline, Joel Univ Colorado Cooperat Inst Res Environm Sci Boulder CO 80309 USA NOAA Earth Syst Res Lab 325 BroadwayMS PSD3 Boulder CO 80305 USA IM Syst Grp Inc College Pk MD USA NOAA NWS Environm Modeling Ctr College Pk MD USA Dept Energy Off Energy Efficiency & Renewable Energy Washington DC USA

During the summer of 2004 a network of 11 wind profiling radars (WPRs) was deployed in New England as part of the New England Air Quality Study (NEAQS). Observations from this dataset are used to determine their impact on numerical weather prediction (NWP) model skill at simulating coastal and offshore winds through data-denial experiments. This study is a part of the Position of Offshore Wind Energy Resources (POWER) experiment, a Department of Energy (DOE) sponsored project that uses National Oceanic and Atmospheric Administration (NOAA) models for two 1-week periods to measure the impact of the assimilation of observations from 11 inland WPRs. Model simulations with and without assimilation of the WPR data are compared at the locations of the inland WPRs, as well as against observations from an additional WPR and a high-resolution Doppler lidar (HRDL) located on board the Research Vessel Ronald H. Brown (RHB), which cruised the Gulf of Maine during the NEAQS experiment. Model evaluation in the lowest 2 km above the ground shows a positive impact of the WPR data assimilation from the initialization time through the next five to six forecast hours at the WPR locations for 12 of 15 days analyzed, when offshore winds prevailed. A smaller positive impact at the RHB ship track was also confirmed. For the remaining three days, during which time there was a cyclone event with strong onshore wind flow, the assimilation of additional observations had a negative impact on model skill. Explanations for the negative impact are offered.

关键词： Observational techniques and algorithms Data quality control Lidars/Lidar observations Profilers atmospheric models and modeling Model comparison Model evaluation/performance Applications Renewable energy

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Effects of a Warming Climate on Daily Snowfall Events in the Northern Hemisphere

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JOURNAL OF CLIMATE 2016年第17期29卷 6295-6318页

作者： Danco, James F. DeAngelis, Anthony M. Raney, Bryan K. Broccoli, Anthony J. Rutgers State Univ Dept Environm Sci 14 Coll Farm Rd New Brunswick NJ 08901 USA Univ Calif Los Angeles Dept Atmospher & Ocean Sci Los Angeles CA 90095 USA Rutgers State Univ Inst Earth Ocean & Atmospher Sci New Brunswick NJ 08901 USA

Using simulations performed with 24 coupled atmosphere ocean global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5), projections of Northern Hemisphere daily snowfall events under the RCP8.5 emissions scenario are analyzed for the periods of 2021-50 and 2071-2100 and compared to the historical period of 1971-2000. The overall frequency of daily snowfall events is simulated to decrease across much of the Northern Hemisphere, except at the highest latitudes such as northern Canada, northern Siberia, and Greenland. Seasonal redistributions of daily snowfall event frequency and average daily snowfall are also projected to occur in some regions. For example, large portions of the Northern Hemisphere, including much of Canada, Tibet, northern Scandinavia, northern Siberia, and Greenland, are projected to experience increases in average daily snowfall and event frequency in midwinter. But in warmer months, the regions with increased snowfall become fewer in number and are limited to northern Canada, northern Siberia, and Greenland. These simulations also show changes in the frequency distribution of daily snowfall event intensity, including an increase in heavier snowfall events even in some regions where the overall snowfall decreases. The projected changes in daily snowfall event frequency exhibit some dependence on the temperature biases of the individual models in certain regions and times of the year, with colder models typically toward the positive end of the distribution of event frequency changes and warmer models toward the negative end, particularly in regions near the transition zone between increasing and decreasing snowfall.

关键词： Geographic location/entity Northern Hemisphere Physical Meteorology and Climatology Climate change Climate prediction models and modeling Climate models Model evaluation/performance

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Operational Wave Prediction System at Environment Canada: Going Global to Improve Regional Forecast Skill

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WEATHER AND FORECASTING 2016年第2期31卷 353-370页

作者： Bernier, Natacha B. Alves, Jose-Henrique G. M. Tolman, Hendrik Chawla, Arun Peel, Syd Pouliot, Benoit Belanger, Jean-Marc Pellerin, Pierre Lepine, Mario Roch, Michel Environm Canada Rech Previs Numer Environm 2121 Route Trans Canadienne Dorval PQ H9P 1J3 Canada NOAA Ctr Weather & Climate Predict College Pk MD USA Environm Canada Serv Informat Rech Dorval PQ Canada

A global deterministic wave prediction system (GDWPS) is used to improve regional forecasts of waves off the Canadian coastline and help support the practice of safe marine activities in Canadian waters. The wave model has a grid spacing of 1/4 degrees with spectral resolution of 36 frequency bins and 36 directional bins. The wave model is driven with hourly 10-m winds generated by the operational global atmospheric prediction system. Ice conditions are updated every three hours using the ice concentration forecasts generated by the Global Ice-Ocean Prediction System. Wave forecasts are evaluated over two periods from 15 August to 31 October 2014 and from 15 December 2014 to 28 February 2015, as well as over select cases during the fall of 2012. The global system is shown to improve wave forecast skill over regions where forecasts were previously produced using limited-area models only. The usefulness of a global expansion is demonstrated for large swell events affecting the northeast Pacific. The first validation of a Canadian operational wave forecast system in the Arctic is presented. Improvements in the representation of forecast wave fields associated with tropical cyclones are also demonstrated. Finally, the GDWPS is shown to result in gains of at least 12 h of lead time.

关键词： Forecasting Forecast verification/skill Operational forecasting models and modeling Ocean models

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Convective Initiation near the Andes in Subtropical South America

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MONTHLY WEATHER REVIEW 2016年第6期144卷 2351-2374页

作者： Rasmussen, K. L. Houze, R. A., Jr. Natl Ctr Atmospher Res Mesoscale & Microscale Meteorol Lab POB 3000 Boulder CO 80307 USA Univ Washington Dept Atmospher Sci Seattle WA 98195 USA

Satellite radar and radiometer data indicate that subtropical South America has some of the deepest and most extreme convective storms on Earth. This study uses the full 15-yr TRMM Precipitation Radar dataset in conjunction with high-resolution simulations from the Weather Research and Forecasting Model to better understand the physical factors that control the climatology of high-impact weather in subtropical South America. The occurrence of intense storms with an extreme horizontal dimension is generally associated with lee cyclogenesis and a strengthening South American low-level jet (SALLJ) in the La Plata basin. The orography of the Andes is critical, and model sensitivity calculations removing and/or reducing various topographic features indicate the orographic control on the initiation of convection and its upscale growth into mesoscale convective systems (MCSs). Reduced Andes experiments show more widespread convective initiation, weaker average storm intensity, and more rapid propagation of the MCS to the east (reminiscent of the MCS life cycle downstream of lower mountains such as the Rockies). With reduced Andes, lee cyclogenesis and SALLJ winds are weaker, while they are stronger in increased Andes runs. The presence of the Sierras de Cordoba (secondary mountain range east of the Andes in Argentina) focuses convective initiation and results in more intense storms in experiments with higher Andes. Average CAPE and CIN values for each terrain modification simulation show that reduced Andes runs had lower CIN and CAPE, while increased Andes runs had both stronger CAPE and CIN. From this research, a conceptual model for convective storm environments leading to convective initiation has been developed for subtropical South America.

关键词： Circulation Dynamics Convective storms Mesoscale systems Physical Meteorology and Climatology Orographic effects Storm environments Observational techniques and algorithms Radars Radar observations models and modeling Mesoscale models

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Sources of Uncertainty in Future Projections of the Carbon Cycle

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JOURNAL OF CLIMATE 2016年第20期29卷 7203-7213页

作者： Hewitt, Alan J. Booth, Ben B. B. Jones, Chris D. Robertson, Eddy S. Wiltshire, Andy J. Sansom, Philip G. Stephenson, David B. Yip, Stan Met Off Hadley Ctr Fitzroy Rd Exeter EX1 3PB Devon England Univ Exeter Exeter Climate Syst Exeter Devon England Hong Kong Polytech Univ Dept Appl Math Hong Kong Hong Kong Peoples R China

The inclusion of carbon cycle processes within CMIP5 Earth system models provides the opportunity to explore the relative importance of differences in scenario and climate model representation to future land and ocean carbon fluxes. A two-way analysis of variance (ANOVA) approach was used to quantify the variability owing to differences between scenarios and between climate models at different lead times. For global ocean carbon fluxes, the variance attributed to differences between representative concentration pathway scenarios exceeds the variance attributed to differences between climate models by around 2025, completely dominating by 2100. This contrasts with global land carbon fluxes, where the variance attributed to differences between climate models continues to dominate beyond 2100. This suggests that modeled processes that determine ocean fluxes are currently better constrained than those of land fluxes;thus, one can be more confident in linking different future socioeconomic pathways to consequences of ocean carbon uptake than for land carbon uptake. The contribution of internal variance is negligible for ocean fluxes and small for land fluxes, indicating that there is little dependence on the initial conditions. The apparent agreement in atmosphere-ocean carbon fluxes, globally, masks strong climate model differences at a regional level. The North Atlantic and Southern Ocean are key regions, where differences in modeled processes represent an important source of variability in projected regional fluxes.

关键词： Geographic location/entity North Atlantic Ocean Southern Ocean Physical Meteorology and Climatology Carbon cycle Mathematical and statistical techniques Bayesian methods Variational analysis models and modeling General circulation models

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Application of the WRF-LETKF Data Assimilation System over Southern South America: Sensitivity to Model Physics

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WEATHER AND FORECASTING 2016年第1期31卷 217-236页

作者： Dillon, Maria E. Skabar, Yanina Garcia Ruiz, Juan Kalnay, Eugenia Collini, Estela A. Echevarria, Pablo Saucedo, Marcos Miyoshi, Takemasa Kunii, Masaru Consejo Nacl Invest Cient & Tecn Natl Meteorol Serv RA-1033 Buenos Aires DF Argentina Univ Buenos Aires Dept Atmospher & Ocean Sci Buenos Aires DF Argentina UMI IFAECI Buenos Aires DF Argentina Univ Buenos Aires CONICET Dept Atmospher & Ocean Sci CIMA Buenos Aires DF Argentina Univ Maryland Dept Atmospher & Ocean Sci College Pk MD 20742 USA Naval Hydrog Serv Buenos Aires DF Argentina Natl Meteorol Serv 25 Mayo 658 C1002ABL Buenos Aires DF Argentina RIKEN Adv Inst Computat Sci Kobe Hyogo Japan Meteorol Res Inst 1-1 Nagamine Tsukuba Ibaraki 305 Japan

Improving the initial conditions of short-range numerical weather prediction (NWP) models is one of the main goals of the meteorological community. Development of data assimilation and ensemble forecast systems is essential in any national weather service (NWS). In this sense, the local ensemble transform Kalman filter (LETKF) is a methodology that can satisfy both requirements in an efficient manner. The Weather Research and Forecasting (WRF) Model coupled with the LETKF, developed at the University of Maryland, College Park, have been implemented experimentally at the NWS of Argentina [Servicio Meteorologico Nacional (SMN)], but at a somewhat lower resolution (40 km) than the operational Global Forecast System (GFS) at that time (27 km). The purpose of this work is not to show that the system presented herein is better than the higher-resolution GFS, but that its performance is reasonably comparable, and to provide the basis for a continued improved development of an independent regional data assimilation and forecasting system. The WRF-LETKF system is tested during the spring of 2012, using the prepared or quality controlled data in Binary Universal Form for Representation of Meteorological Data (PREPBUFR) observations from the National Centers for Environmental Prediction (NCEP) and lateral boundary conditions from the GFS. To assess the effect of model error, a single-model LETKF system (LETKF-single) is compared with a multischeme implementation (LETKF-multi), which uses different boundary layer and cumulus convection schemes for the generation of the ensemble of forecasts. The performance of both experiments during the test period shows that the LETKF-multi usually outperforms the LETKF-single, evidencing the advantages of the use of the multischeme approach. Both data assimilation systems are slightly worse than the GFS in terms of the synoptic environment representation, as could be expected given their lower resolution. Results from a case study of a stron

关键词： Kalman filters Mathematical and statistical techniques Model initialization models and modeling Model evaluation/performance Forecasting Data assimilation Numerical weather prediction/forecasting

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Roles of an Atmospheric River and a Cutoff Low in the Extreme Precipitation Event in Hiroshima on 19 August 2014

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MONTHLY WEATHER REVIEW 2016年第3期144卷 1145-1160页

作者： Hirota, Nagio Takayabu, Yukari N. Kato, Masaya Arakane, Sho Univ Tokyo Natl Inst Polar Res Tokyo Japan Univ Tokyo Atmosphere & Ocean Res Inst Tokyo Japan Nagoya Univ Hydrospher Atmospher Res Ctr Nagoya Aichi 4648601 Japan Geosphere Environm Technol Corp Tokyo Japan

Precipitation in excess of 100 mm h(-1) in Hiroshima, Japan, on 19 August 2014, caused a flash flood that resulted in 75 deaths and destroyed 330 houses. This study examined the meteorological background of this fatal flood. During this event, considerable filamentary transport of water vapor from the Indochina Peninsula to the Japanese islands occurred, forming a so-called atmospheric river (AR). This AR had a deep structure with an amount of free tropospheric moisture comparable with that of the boundary layer. Furthermore, a cutoff low (COL), detached from the subtropical jet over the central Pacific, moved northwestward to the Japanese islands. Instability associated with the cold core of the COL and dynamical ascent induced in front of it, interacted with the free tropospheric moisture of the AR, which caused the considerable precipitation in Hiroshima. Moreover, the mountains of the Japanese islands played a role in localizing the precipitation in Hiroshima. These roles were separately evaluated on the basis of sensitivity experiments with a cloud-resolving model.

关键词： Precipitation Atm/Ocean Structure/ Phenomena Mesoscale models models and modeling Circulation/ Dynamics Extreme events Potential vorticity

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