The marine boundary layer of the northeastern U.S. is studied with focus on wind speed, atmospheric stability, and turbulent kinetic energy (TKE), the three most relevant properties in the context of ...offshore wind power development. Two long‐term observational data sets are analyzed. The first one consists of multilevel meteorological variables measured up to 60 m during 2003–2011 at the offshore Cape Wind tower, located near the center of the Nantucket Sound. The second data set comes from the 2013–2014 IMPOWR campaign (Improving the Modeling and Prediction of Offshore Wind Resources), in which wind and wave data were collected with new instruments on the Cape Wind platform, in addition to meteorological data measured during 19 flight missions offshore of New York, Connecticut, Rhode Island, and Massachusetts. It is found that, in this region: (1) the offshore wind resource is remarkable, with monthly average wind speeds at 60 m exceeding 7 m s−1 all year round, highest winds in winter (10.1 m s−1) and lowest in summer (7.1 m s−1), and a distinct diurnal modulation, especially in summer; (2) the marine boundary layer is predominantly unstable (61% unstable vs. 21% neutral vs. 18% stable), meaning that mixing is strong, heat fluxes are positive, and the wind speed profile is often nonlogarithmic (~40% of the time); and (3) the shape of the wind speed profile (log versus nonlog) is an effective qualitative proxy for atmospheric stability, whereas TKE alone is not.
Key Points
The marine boundary layer offshore of the northeastern U.S. is predominantly unstable
Nonlogarithmic wind speed profiles are a valid proxy for unstable offshore conditions
Stable conditions offshore of the northeastern U.S. occur mostly in spring and with southwesterly flow
The wind resource offshore of the East Coast of the United States is well known for its potential to provide abundant, clean, renewable, and domestic electricity. However, limited observations from ...this region are recorded at heights above the water that penetrate significantly into the planetary boundary layer (PBL). As a result, mesoscale models have been used to characterize the offshore wind resource in this region but have not been evaluated fully within the PBL due to the scarcity of observations. This paper describes the setup and some early results from the Improving the Mapping and Prediction of Offshore Wind Resources (IMPOWR) field study conducted in the Nantucket Sound area in 2013/14. The IMPOWR campaign provides a rich dataset of observations within the PBL from a variety of sources: high-frequency Long-EZ aircraft, a multilevel atmospheric and oceanic tower in Nantucket Sound, and lidars on the south shore of eastern Long Island and Block Island. In addition to new data for model validation and wind resource assessment, the IMPOWR field campaign provides new insights on meteorological features important for wind power development, such as the New York Bight jet and shallow marine layer.
The northeast U.S. extratropical cyclone of 8–9 February 2013 produced blizzard conditions and more than 0.6–0.9 m (2–3 ft) of snow from Long Island through eastern New England. A surprising aspect ...of this blizzard was the development and rapid weakening of a snowband to the northwest of the cyclone center with radar ref lectivity factor exceeding 55 dBZ. Because the radar reflectivity within snowbands in winter storms rarely exceeds 40 dBZ, this event warranted further investigation. The high radar reflectivity was due to mixed-phase microphysics in the snowband, characterized by high differential reflectivity (Z
DR> 2 dB) and low correlation coefficient (CC < 0.9), as measured by the operational dual-polarization radar in Upton, New York (KOKX). Consistent with these radar observations, heavy snow and ice pellets (both sleet and graupel) were observed. Later, as the reflectivity decreased to less than 40 dBZ, surface observations indicated a transition to primarily high-intensity dry snow, consistent with lower-tropospheric cold advection. Therefore, the rapid decrease of the 50+ dBZreflectivity resulted from the transition from higher-density, mixed-phase precipitation to lower-density, dry-snow crystals and aggregates. This case study indicates the value that dual-polarization radar can have in an operational forecast environment for determining the variability of frozen precipitation (e.g., ice pellets, dry snow aggregates) on relatively small spatial scales.
Winds, temperatures and moisture in the planetary boundary layer (PBL) are often difficult for operational models to predict given the relatively sparse observations and that most model PBL ...parameterizations were developed over inland locations. Coastal marine layer forecasts are important for the forecasting of severe storms and wind energy resources in the highly populated coastal marine environment of the Northeast U.S. (NEUS). Mesoscale models are known to have large biases in wind speeds and temperatures at these lower levels over coastal waters. The goal of this project is to evaluate the performance of six PBL schemes in the Weather Research and Forecasting (WRF-ARW) model version 3.4.1 in the coastal marine environment of the NEUS. This study region, stretching from the south shore of Long Island out to Cape Cod is an ideal location for an offshore wind energy grid based on such factors as regional energy demand, water depth, and available wind resource. Verification of six WRF PBL schemes (two non-local, first-order schemes and four local, TKE-order schemes) was performed using a dataset of observations at multiple levels from the Cape Wind tower in Nantucket Sound from 2003 to 2011, as well as surrounding NDBC and ASOS stations. A series of 30-hour WRF runs were conducted for 90 randomly selected days between 2003 and 2011, with initial and boundary conditions supplied by the North American Regional Reanalysis (NARR). All schemes generally displayed negative wind speed biases over the water. The cool season displayed the largest negative biases as well as a shear profile indicative of an over-mixed boundary layer. It is hypothesized that errors in the model SST field in Nantucket Sound aided in the too-stable (unstable) model MABL structures during the warm (cool) seasons and the resultant under-mixed (over-mixed) wind shear profiles. Additional model verification from three Long-EZ aircraft flights during the Improving the Mapping and Prediction of Offshore Wind Resources (IMPOWR) field campaign during strong southwesterly flow and a developing low-level jet (LLJ) supported the hypotheses. WRF simulations show that most schemes underestimated the height and magnitude of the LLJ, while overestimating the static stability below the LLJ in the vicinity of Nantucket Sound. A warmer SST field was found to improve the near-surface thermal and moisture profiles. Model runs were forced with a variety of analyses, and it was found that even for long simulations the results were more sensitive to the boundary conditions than to the PBL schemes.
As it seeks to win the hearts and minds of citizens in the Muslim world, the United States has poured millions of dollars into local television and radio programming, hoping to generate pro-American ...currents on Middle Eastern airwaves. However, as this fascinating new book shows, the Middle Eastern media producers who rely on these funds are hardly puppets on an American string, but instead contribute their own political and creative agendas while working within U.S. restrictions.
Title supplied by cataloger.
Abstract
Background
How severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectivity varies with viral load is incompletely understood. Whether rapid point-of-care antigen lateral flow ...devices (LFDs) detect most potential transmission sources despite imperfect clinical sensitivity is unknown.
Methods
We combined SARS-CoV-2 testing and contact tracing data from England between 1 September 2020 and 28 February 2021. We used multivariable logistic regression to investigate relationships between polymerase chain reaction (PCR)-confirmed infection in contacts of community-diagnosed cases and index case viral load, S gene target failure (proxy for B.1.1.7 infection), demographics, SARS-CoV-2 incidence, social deprivation, and contact event type. We used LFD performance to simulate the proportion of cases with a PCR-positive contact expected to be detected using 1 of 4 LFDs.
Results
In total, 231 498/2 474 066 (9%) contacts of 1 064 004 index cases tested PCR-positive. PCR-positive results in contacts independently increased with higher case viral loads (lower cycle threshold Ct values), for example, 11.7% (95% confidence interval CI 11.5–12.0%) at Ct = 15 and 4.5% (95% CI 4.4–4.6%) at Ct = 30. B.1.1.7 infection increased PCR-positive results by ~50%, (eg, 1.55-fold, 95% CI 1.49–1.61, at Ct = 20). PCR-positive results were most common in household contacts (at Ct = 20.1, 8.7% 95% CI 8.6–8.9%), followed by household visitors (7.1% 95% CI 6.8–7.3%), contacts at events/activities (5.2% 95% CI 4.9–5.4%), work/education (4.6% 95% CI 4.4–4.8%), and least common after outdoor contact (2.9% 95% CI 2.3–3.8%). Contacts of children were the least likely to test positive, particularly following contact outdoors or at work/education. The most and least sensitive LFDs would detect 89.5% (95% CI 89.4–89.6%) and 83.0% (95% CI 82.8–83.1%) of cases with PCR-positive contacts, respectively.
Conclusions
SARS-CoV-2 infectivity varies by case viral load, contact event type, and age. Those with high viral loads are the most infectious. B.1.1.7 increased transmission by ~50%. The best performing LFDs detect most infectious cases.
In 2,474,066 contacts of 1,064,004 SARS-CoV-2 cases, PCR-positive tests in contacts increased with higher index case viral loads, the B.1.1.7 variant and household contact. Children were less infectious. Lateral flow devices detect 83.0-89.5% of infections leading to onward transmission
A new instrument has been proposed for measuring surface air pressure over the marine surface with a combined active/passive scanning multi-channel differential absorption radar (DAR) to provide an ...estimate of the total atmospheric column oxygen content. A demonstrator instrument, the Microwave Barometric Radar and Sounder (MBARS), has been funded by the National Aeronautics and Space Administration (NASA) for airborne test missions. Here, a proof-of-concept study to evaluate the potential impact of spaceborne surface pressure data on numerical weather prediction is performed using the Goddard Modeling and Assimilation Office global observing system simulation experiment (OSSE) framework. This OSSE framework employs the Goddard Earth Observing System model and the hybrid 4D ensemble variational Gridpoint Statistical Interpolation data assimilation system.
Multiple flight and scanning configurations of potential spaceborne orbits are examined. Swath width and observation spacing for the surface pressure data are varied to explore a range of sampling strategies. For wider swaths, the addition of surface pressures reduces the root mean square surface pressure analysis error by as much as 20% over some ocean regions. The forecast sensitivity observation impact tool estimates impacts on the Pacific Ocean basin boundary layer 24-hour forecast temperatures for spaceborne surface pressures on par with rawinsondes and aircraft, and greater impacts than the current network of ships and buoys. The largest forecast impacts are found in the southern hemisphere extratropics.
The synthesis and characterization of a new class of neutral aminyl radicals is reported. Monoradicals were obtained by reduction of azoimidazolium dyes with potassium. Structural, spectroscopic, and ...computational data suggest that the spin density is centered on one of the nitrogen atoms of the former azo group. The reduction of a dimeric dye with an octamethylbiphenylene bridge between the azo groups resulted in the formation of a biradical with largely independent unpaired electrons. Both the monoradicals and the biradical were found to display high stability in solution as well as in the solid state.
PDF
