During the Deep Propagating Gravity Wave Experiment (DEEPWAVE) project in June and July 2014, the Gulfstream V research aircraft flew 97 legs over the Southern Alps of New Zealand and 150 legs over the Tasman Sea and Southern Ocean, mostly in the low stratosphere at 12.1-km altitude. Improved instrument calibration, redundant sensors, longer flight legs, energy flux estimation, and scale analysis revealed several new gravity wave properties. Over the sea, flight-level wave fluxes mostly fell below the detection threshold. Over terrain, disturbances had characteristic mountain wave attributes of positive vertical energy flux (EF z ), negative zonal momentum flux, and upwind horizontal energy flux. In some cases, the fluxes changed rapidly within an 8-h flight, even though environmental conditions were nearly unchanged. The largest observed zonal momentum and vertical energy fluxes were MF x 5 2550 mPa and EF z 5 22 W m 22 , respectively. A wide variety of disturbance scales were found at flight level over New Zealand. The vertical wind variance at flight level was dominated by short ''fluxless'' waves with wavelengths in the 6-15-km range. Even shorter scales, down to 500 m, were found in wave breaking regions. The wavelength of the flux-carrying mountain waves was much longer-mostly between 60 and 150 km. In the strong cases, however, with EF z . 4 W m 22, the dominant flux wavelength decreased (i.e., ''downshifted'') to an intermediate wavelength between 20 and 60 km. A potential explanation for the rapid flux changes and the scale ''downshifting'' is that low-level flow can shift between ''terrain following'' and ''envelope following'' associated with trapped air in steep New Zealand valleys.
The Convective Transport of Active Species in the Tropics (CONTRAST) experiment was conducted from Guam (13.5° N, 144.8° E) during January-February 2014. Using the NSF/NCAR Gulfstream V research aircraft, the experiment investigated the photochemical environment over the tropical western Pacific (TWP) warm pool, a region of massive deep convection and the major pathway for air to enter the stratosphere during Northern Hemisphere (NH) winter. The new observations provide a wealth of information for quantifying the influence of convection on the vertical distributions of active species. The airborne in situ measurements up to 15 km altitude fill a significant gap by characterizing the abundance and altitude variation of a wide suite of trace gases. These measurements, together with observations of dynamical and microphysical parameters, provide significant new data for constraining and evaluating global chemistry climate models. Measurements include precursor and product gas species of reactive halogen compounds that impact ozone in the upper troposphere/lower stratosphere. High accuracy, in-situ measurements of ozone obtained during CONTRAST quantify ozone concentration profiles in the UT, where previous observations from balloon-borne ozonesondes were often near or below the limit of detection. CONTRAST was one of the three coordinated experiments to observe the TWP during January-February 2014. Together, CONTRAST, ATTREX and CAST, using complementary capabilities of the three aircraft platforms as well as ground-based instrumentation, provide a comprehensive quantification of the regional distribution and vertical structure of natural and pollutant trace gases in the TWP during NH winter, from the oceanic boundary to the lower stratosphere.
e d m a n * Smog c h e c k data o n 307 of these vehicles.Of these, 126 (41%) showed deliberate tampering, and another 77 (25%) had defective or ~nissi~lg equiptnent that tnay not have been the result of tampering (for ex-I n response to continuing pollution prob-lected 91,679 records with valid H C and ample, missing air pump belts). Overall, 282 lems, in 1990 Congress passed the Clean CO tneasurements (8). T h e etnission distri-(92%) failed the inspection even though all Air A c t Amendments, many parts of which bution is highly skewed; the half of the fleet had valid registrations. Thus, less than 8% deal with motor vehicles. Motor vehicles are with the lowest emissio~ls contributed less of the vehicles identified as gross polluters the ~r i m a r v source of urban carbon tnonox-than 10% of the C O and HC. while a few bv remote sensine nassed a n immediate " L ide (CO) and are an important source of the high-emission vehicles dominated the rdadside test. W h e n r a~l d o~n pullover studhvdrocarbons I H C ) and oxides of nitrogen mean values. I n this instance. 7% of the ies were carried out bv the California BLI--(NO,) that are responsible for the fortnation of photochemical stnog and ground-level ozone (1). Cost estimates for itnplenlenting the act's mobile source provisions range up to $1 2 billion annuallv 12). Thus it is im-,~, portant to analyze the scientific basis for these legislative programs (1 ).For any region violating air quality standards, a State Itnolenle~ltation Plan (SIP) , , must be submitted to and approved by the U.S. Environmental Protection Agency (EPA). In approving the SIP, EPA grants credit for each portion of the plan, including new vehicle emission standards, new fuels, vehicle scrappage, and inspection and maintenance (IM) programs, o n the basis of predictions from a spreadsheet computer tnodel 13). This EPA model treats all cars of ~, a given tnodel year as having the same odometer reading, the same annual mileage accutnulation, and an equal likelihood of emission control systetn probletns. T h e model has had little success in predicting urban on-road vehicle etnissions (4), and the use of unverified computer models as the sole guide for public policy decisions is controversial (5). Calvert et al. (6) criticized the tnodel and recommended in-use vehicles accounted for 50% of'the on-road C O emissions, and 10% of the vehicles accou~lted for 50% of the on-road HC etnissions. These vehicles we call gross polluters. About 5% of the vehicles were gross polluters for both HC and CO (9).It is often assumed that gross poll~tters are sitnply old vehicles. In fact, all model vears of vehicles we have measured o n the road include some proportion of gross polluters, as shown in Fig. l. W e found that the highest emitting 20% of the newest cars were worse polluters than the lowest emitting 40% of vehicles from any tnodel year, even those from model years before the advent of catalytic converters (1970 and earlier). These data are typical of CO and H C results across the United States an...
The Cloud System Evolution in the Trades (CSET) study was designed to describe and explain the evolution of the boundary layer aerosol, cloud, and thermodynamic structures along trajectories within the North Pacific trade winds. The study centered on seven round trips of the National Science Foundation–National Center for Atmospheric Research (NSF–NCAR) Gulfstream V (GV) between Sacramento, California, and Kona, Hawaii, between 7 July and 9 August 2015. The CSET observing strategy was to sample aerosol, cloud, and boundary layer properties upwind from the transition zone over the North Pacific and to resample these areas two days later. Global Forecast System forecast trajectories were used to plan the outbound flight to Hawaii with updated forecast trajectories setting the return flight plan two days later. Two key elements of the CSET observing system were the newly developed High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) and the high-spectral-resolution lidar (HSRL). Together they provided unprecedented characterizations of aerosol, cloud, and precipitation structures that were combined with in situ measurements of aerosol, cloud, precipitation, and turbulence properties. The cloud systems sampled included solid stratocumulus infused with smoke from Canadian wildfires, mesoscale cloud–precipitation complexes, and patches of shallow cumuli in very clean environments. Ultraclean layers observed frequently near the top of the boundary layer were often associated with shallow, optically thin, layered veil clouds. The extensive aerosol, cloud, drizzle, and boundary layer sampling made over open areas of the northeast Pacific along 2-day trajectories during CSET will be an invaluable resource for modeling studies of boundary layer cloud system evolution and its governing physical processes.
[1] Microphysical properties of cirrus clouds largely influence their atmospheric radiative forcing. However, uncertainties remain in simulating/parameterizing the evolution of ice crystals. These uncertainties require more analyses in the Lagrangian view, yet most in situ observations are in the Eulerian view. Here we demonstrate a new method to separate out five phases of ice crystal evolution, using the horizontal spatial relationships between ice supersaturated regions (ISSRs) and ice crystal regions (ICRs). Based on global in situ data sets, we show that the samples of clear-sky ISSRs, ice crystal formation/growth, and evaporation/sedimentation are~20%, 10%, and 70% of the total ISSR + ICR samples, respectively. In addition, the variance of number-weighted mean diameter (Dc) becomes narrower during the evolution, while the distribution of ice crystal number density (Nc) becomes wider. The new method helps to understand the evolution of ICRs and ISSRs on the microscale by using in situ Eulerian observations.
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