AbstractAlthough atmospheric observing systems were already an important part of meteorology before the American Meteorological Society was established in 1919, the past 100 years have seen a stead...

A two-look airborne Doppler wind lidar operating at the 532-nm laser wavelength, the Green Optical Autocovariance Wind Lidar (GrOAWL), was built and flown aboard the NASA WB-57 research aircraft. Flight campaign goals were to validate the instrument wind measurements and to demonstrate the two-look measurement concept proposed for spaceborne mission concepts such as the Atmospheric Transport, Hurricanes, and Extratropical Numerical Weather Prediction with the Optical Autocovariance Wind Lidar (ATHENA-OAWL) mission. The GrOAWL-measured winds were compared with collocated dropsonde measurements. Line-of-sight velocity (LOSV) measurements for the individual GrOAWL looks showed excellent agreement with dropsondes (R-2 > 0.9). The LOSV biases were very small and not statistically different from 0 m s(-1) at the 95% confidence interval (-0.07 +/- 0.07 m s(-1) and 0.01 +/- 0.07 m s(-1) for look 1 and look 2, respectively). The wind speed and direction profiles retrieved by combining the two GrOAWL looks were also in very good agreement (R-2 > 0.85). An instrument performance model indicated the instrument wind measurement precision was likely lowered (uncertainty was increased) by a factor of similar to 3.3 during the flights relative to predicted as built instrument performance. The reduced performance was not observed during ground-based atmospheric testing and thus has been attributed to impacts of the harsh operating conditions of the WB-57 aircraft (high vibration, thermal gradients, and high humidity). The exercise of scaling the GrOAWL instrument performance and grid scale to space showed space-based OAWL wind measurements would yield products with precision at least as good as the GrOAWL instrument.

AbstractForecast errors with respect to wind, temperature, moisture, clouds, and precipitation largely correspond to the limited capability of current Earth system models to capture and simulate land–atmosphere feedback. To facilitate its realistic simulation in next-generation models, an improved process understanding of the related complex interactions is essential. To this end, accurate 3D observations of key variables in the land–atmosphere (L–A) system with high vertical and temporal resolution from the surface to the free troposphere are indispensable.Recently, we developed a synergy of innovative ground-based, scanning active remote sensing systems for 2D to 3D measurements of wind, temperature, and water vapor from the surface to the lower troposphere that is able to provide comprehensive datasets for characterizing L–A feedback independently of any model input. Several new applications are introduced, such as the mapping of surface momentum, sensible heat, and latent heat fluxes in heterogeneous terrain; the testing of Monin–Obukhov similarity theory and turbulence parameterizations; the direct measurement of entrainment fluxes; and the development of new flux-gradient relationships. An experimental design taking advantage of the sensors’ synergy and advanced capabilities was realized for the first time during the Land Atmosphere Feedback Experiment (LAFE), conducted at the Atmospheric Radiation Measurement Program Southern Great Plains site in August 2017. The scientific goals and the strategy of achieving them with the LAFE dataset are introduced. We envision the initiation of innovative L–A feedback studies in different climate regions to improve weather forecast, climate, and Earth system models worldwide.

The atmospheric flow phenomenon known as the Low Level Jet (LLJ) is an important source of wind power production in the Great Plains. However, due to the lack of measurements with the precision and vertical resolution needed, particularly at rotor heights, it is not well-characterized or understood in offshore regions being considered for wind-farm development. The present paper describes the properties of LLJs and wind shear through the rotor layer of a hypothetical wind turbine, as measured from a ship-borne Doppler lidar in the Gulf of Maine in July-August 2004. LLJs, frequently observed below 600m, were mostly during nighttime and transitional periods, but they were also were seen during some daytime hours. The presence of a LLJ significantly modified wind profiles producing vertical wind speed shear. When the wind shear was strong, the estimates of wind power based upon wind speeds measured at hub-height could have significant errors. Additionally, the inference of hub-height winds from near-surface measurements may introduce further error in the wind power estimate. The lidar dataset was used to investigate the uncertainty of the simplified power-law relation that is often employed in engineering approaches for the extrapolation of surface winds to higher elevations. The results show diurnal and spatial variations of the shear exponent empirically found from surface and hub-height measurements. Finally, the discrepancies between wind power estimates using lidar-measured hub-height winds and rotor equivalent winds are discussed. Copyright (c) 2016 John Wiley & Sons, Ltd.

This paper gives a proper study of 11 types of Weibull parameters estimation methods and their performance comparison for wind potential assessment on India's first offshore project in the Gulf of Khambhat, Gujarat. The Lidar (up to 200 m) and met mast (up to 100 m) are deployed to record wind data from Nov-2017 to Dec-2019 by the National Institute of Wind Energy (NIWE), Government of India. The estimation methods such as, modified maximum likelihood method (MMLM), maximum likelihood method (MLM), empirical method of Justus (EMJ), empirical method of Lysen (EML), graphical method (GM), first method of moment (MOM-1), second method of moment (MOM-2), third method of moment (MOM-3), alternative maximum likelihood method (AMLM), WAsP or equivalent energy method (EEM), energy pattern factor method (EPFM), found in literature survey are compared to evaluate the performance using statistical methods in the offshore region of India. The mathematical expressions of methods have been coded and implemented by MATLAB software through a proper data analysis. There is a need to explore more appropriate probabilistic distribution than Weibull distribution. The MMLM, MLM, and MOM versions perform nicely, followed by the empirical method of Justus and Lysen. The GM method underperformed and that needs modification.

We have observed lower nitrogen dioxide (NO2) and ozone (O3) during a hot weekend (summer 2010) from aircraft over the entire South Coast Air Basin (SoCAB). Surface concentrations of NO2, O3, and temperature from 1996 to 2014 corroborate that this lower O3 on weekends is increasingly likely in recent years. While higher surface O3 on the weekends (weekend ozone effect, WO3E) remains widespread, the spatial extent and the trend in the probability of WO3E occurrences (PWO3E) have decreased significantly compared to a decade ago. This decrease is mostly the result of lower O3 on hot weekends in recent years. PWO3E is lowest in the eastern SoCAB. The major decrease happened during the 2008 economic recession, after which PWO3E has stabilized at a 15–25% lower level throughout most of the basin. Future NOx reductions are likely to be increasingly effective at reducing O3 pollution initially under hot conditions in the coming decade.

Offshore wind power is an important source of renewable energy. It is crucial to have reliable data for wind resource assessment and understanding of wind-flow variability to locate, design and operate wind farms correctly. Currently, new technologies based on lidar measurements from different mooring/floating/fixed platforms are emerging on the wind energy market. These technologies are aimed at providing cost effective data through the layer swept by modern turbine rotor blades, if they succeed in overcoming measurement errors related to the ocean motion. Thus, developing motion compensation techniques and validating the accuracy of lidar measurements offshore is a big engineering challenge.

The California Research at the Nexus of Air Quality and Climate Change (CalNex) field study was conducted throughout California in May, June, and July of 2010. The study was organized to address issues simultaneously relevant to atmospheric pollution and climate change, including (1) emission inventory assessment, (2) atmospheric transport and dispersion, (3) atmospheric chemical processing, and (4) cloud‐aerosol interactions and aerosol radiative effects. Measurements from networks of ground sites, a research ship, tall towers, balloon‐borne ozonesondes, multiple aircraft, and satellites provided in situ and remotely sensed data on trace pollutant and greenhouse gas concentrations, aerosol chemical composition and microphysical properties, cloud microphysics, and meteorological parameters. This overview report provides operational information for the variety of sites, platforms, and measurements, their joint deployment strategy, and summarizes findings that have resulted from the collaborative analyses of the CalNex field study. Climate‐relevant findings from CalNex include that leakage from natural gas infrastructure may account for the excess of observed methane over emission estimates in Los Angeles. Air‐quality relevant findings include the following: mobile fleet VOC significantly declines, and NO x emissions continue to have an impact on ozone in the Los Angeles basin; the relative contributions of diesel and gasoline emission to secondary organic aerosol are not fully understood; and nighttime NO 3 chemistry contributes significantly to secondary organic aerosol mass in the San Joaquin Valley. Findings simultaneously relevant to climate and air quality include the following: marine vessel emissions changes due to fuel sulfur and speed controls result in a net warming effect but have substantial positive impacts on local air quality.

Substantial uncertainties still exist in the scientific understanding of the possible interactions between urban and natural (biogenic) emissions in the production and transformation of atmospheric aerosol and the resulting impact on climate change. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Carbonaceous Aerosol and Radiative Effects Study (CARES) carried out in June 2010 in Central Valley, California, was a comprehensive effort designed to improve this understanding. The primary objective of the field study was to investigate the evolution of secondary organic and black carbon aerosols and their climate-related properties in the Sacramento urban plume as it was routinely transported into the forested Sierra Nevada foothills area. Urban aerosols and trace gases experienced significant physical and chemical transformations as they mixed with the reactive biogenic hydrocarbons emitted from the forest. Two heavily-instrumented ground sites – one within the Sacramento urban area and another about 40 km to the northeast in the foothills area – were set up to characterize the evolution of meteorological variables, trace gases, aerosol precursors, aerosol size, composition, and climate-related properties in freshly polluted and "aged" urban air. On selected days, the DOE G-1 aircraft was deployed to make similar measurements upwind and across the evolving Sacramento plume in the morning and again in the afternoon. The NASA B-200 aircraft, carrying remote sensing instruments, was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties within and around the plume. This overview provides: (a) the scientific background and motivation for the study, (b) the operational and logistical information pertinent to the execution of the study, (c) an overview of key observations and initial findings from the aircraft and ground-based sampling platforms, and (d) a roadmap of planned data analyses and focused modeling efforts that will facilitate the integration of new knowledge into improved representations of key aerosol processes and properties in climate models.

The NOAA Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar is a differential absorption lidar (DIAL) for measuring ozone concentration and aerosol backscatter profiles that was originally designed for nadir-looking operation from an airborne platform. In order to expand the capabilities of this system, we have reconfigured the TOPAZ system for ground-based zenith-looking operation and have constructed an optical scanner to allow measurements at low pointing angles (0-30 degrees). In this new configuration, TOPAZ is capable of making measurements from ground level to several kilometers altitude with high vertical resolution near the ground. The (reversibly) reconfigured system has been installed in a truck and was deployed to the Uintah Basin Winter Ozone Study (UBWOS) experiment in eastern Utah, USA. The TOPAZ lidar modifications and the new scanner are described, and data acquired in this new configuration are presented. 1. BRIEF LIDAR DESCRIPTION The NOAA TOPAZ lidar [1], [2] is designed around an all solid state Ce:LiCAF-based laser which is tunable from 285-310 nm. The system is operated with three output wavelengths tuned sequentially on a pulse-topulse basis to provide the signals needed for a DIAL measurement of ozone profiles along with aerosol backscatter profiles. The pulses are ~100 ns wide, the pulse rate is 1000 Hz, and the combined output of the three wavelengths is ~100 mW. The laser beam is transmitted coaxially with the receiver telescope. The receiver portion of the lidar uses a 0.5 m diameter telescope to collect the backscattered light and photomultiplier tubes for detection in two channels (near-field and far-field). The signals from these two channels are digitized and accumulated in a custom field programmable gate array (FPGA)-based data acquisition system. The digitized signals are then saved to disk and processed using a first-cut analysis for realtime display to the lidar operators. An iterative DIAL analysis technique was developed for this system to calculate the ozone and aerosol profiles and to remove effects on the ozone profiles due to differential aerosol backscatter and extinction. In its airborne (nadir-looking) configuration, TOPAZ is capable of measuring ozone with 90-m and 10-s resolution along the lidar line-of-sight with <5% typical and up to 15% accuracy [2] depending on the total atmospheric attenuation along the measurement path. Uncalibrated aerosol backscatter profiles are measured with 18-m resolution for the same 10-s interval. For both measurements, the profiles start ~400 m from the lidar (limited by transmitter-to-receiver overlap) and can extend up to 5000 m range. Significantly more details of the airborne configuration of the TOPAZ lidar and the analysis of its signals may be found in [1] and [2]. 2. RECONFIGURATION FOR GROUND-

The influence of stratosphere‐to‐troposphere transport (STT) on surface ozone (O3) concentrations in the greater Los Angeles area during the CalNex and IONS‐2010 measurement campaigns has been investigated. Principal component analysis (PCA) of surface O3measurements from 41 sampling stations indicates that ∼13% of the variance in the maximum daily 8‐h average (MDA8) O3between May 10 and June 19, 2010 was associated with changes of 2–3 day duration linked to the passage of upper‐level troughs. Ozonesondes launched from Joshua Tree National Park and airborne lidar measurements show that these changes coincided with the appearance of stratospheric intrusions in the lower troposphere above southern California. The Lagrangian particle dispersion model FLEXPART reproduces most of these intrusions, and supports the conclusion from the PCA that significant transport of stratospheric air to the surface occurred on May 28–30. This intrusion led to a peak 1‐h O3 concentration of 88 ppbv at Joshua Tree National Monument near the ozonesonde launch site on May 28, and widespread entrainment of stratospheric air into the boundary layer increased the local background O3 over the entire area to ∼55 ppbv on May 29–30. This background was 10–15 ppbv higher than the baseline O3 in air transported ashore from the Pacific Ocean, and when combined with locally produced O3 led to several exceedances of the current National Ambient Air Quality Standard (NAAQS) on the following day.

The National Oceanic and Atmospheric Administration/Earth System Research Laboratory/Chemical Sciences Division (NOAA/ESRL/CSD) has developed a versatile, airborne lidar system for measuring ozone and aerosols in the boundary layer and lower free troposphere. The Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) lidar was deployed aboard a NOAA Twin Otter aircraft during the Texas Air Quality Study (TexAQS 2006) and the California Research at the Nexus of Air Quality and Climate Change (CalNex 2010) field campaigns. TOPAZ is capable of measuring ozone concentrations in the lower troposphere with uncertainties of several parts per billion by volume at 90-m vertical and 600-m horizontal resolution from an aircraft flying at 60 m s(-1). The system also provides uncalibrated aerosol backscatter profiles at 18-m vertical and 600-m horizontal resolution. TOPAZ incorporates state-of-the-art technologies, including a cerium-doped lithium calcium aluminum fluoride (Ce:LiCAF) laser, to make it compact and lightweight with low power consumption. The tunable, three-wavelength UV laser source makes it possible to optimize the wavelengths for differing atmospheric conditions, reduce the interference from other atmospheric constituents, and implement advanced analysis techniques. This paper describes the TOPAZ lidar, its components and performance during testing and field operation, and the data analysis procedure, including a discussion of error sources. The performance characteristics are illustrated through a comparison between TOPAZ and an ozonesonde launched during the TexAQS 2006 field campaign. A more comprehensive set of comparisons with in situ measurements during TexAQS 2006 and an assessment of the TOPAZ accuracy and precision are presented in a companion paper.

The NOAA airborne ozone lidar system [Tunable Optical Profiler for Aerosol and Ozone (TOPAZ)] is compared with the fast-response chemiluminescence sensor flown aboard the NOAA WP-3D during the 2006 Texas Air Quality Study (TexAQS). TOPAZ measurements made from the NOAA Twin Otter, flying at an altitude of similar to 3300 m MSL in the Houston, Texas, area on 31 August, and the Dallas, Texas, area on 13 September, show that the overall uncertainty in the 10-s (similar to 600-m horizontal resolution) TOPAZ profiles is dominated by statistical uncertainties (1 sigma) of similar to 8 ppbv (6%-10%) at ranges of similar to 2300 m from the aircraft (similar to 1000 m MSL), and similar to 11-27 ppbv (12%-30%) at ranges of similar to 2800 m (similar to 500 m MSL). These uncertainties are substantially reduced by spatial averaging, and the averages of 11 profiles (of 110 s or 6.6-km horizontal resolution) at similar to 1000 m MSL are in excellent agreement (+/- 2%) with the in situ measurements at similar to 500 m MSL. The TOPAZ measurements at lower altitudes on 31 August exhibit a negative bias of up to similar to 15%, however, when the lidar signals were strongly attenuated by very high ozone levels in the plume from the Houston Ship Channel. This bias appears to result from nonlinear behavior in the TOPAZ signal amplifiers, which is described in the companion paper by Alvarez et al. An empirical correction is presented.