Abstract

The horizontal structure and dynamical properties of the teleconnection patterns in the interannual variability of the Northern Hemisphere wintertime 500 mb height field are investigated. Regression maps based on indices for the eastern Atlantic (EA), Pacific/North American (PNA), western Atlantic (WA), western Pacific (WP) and Eurasian (EU) patterns defined by Wallace and Gutzler are used to define the geographically fixed patterns. Space-spectrum analysis including a spherical harmonic decomposition is applied to these maps. Anomalous geostrophic wind fields derived from these regression maps are used to estimate the kinetic energy conversion between the climatological mean state and the wave structures associated with the teleconnection patterns.

The teleconnection patterns comprise “seesaw” and/or wavelike structures. In general, the kinetic energy of the teleconnection patterns is concentrated in total wavenumber n = 5 and 6 components with zonal wavenumbers m = 0, 1 and 2, which correspond to zonally elongated “seesaw” structures near the jetstreams. The phase tilt of the wave axes indicates that some wavecomponents of the Atlantic teleconnection patterns (EA, WA and EU) propagate wave energy equatorward, whereas the ultralong wavecomponents of the Pacific patterns (PNA and WP) exhibit poleward energy dispersion, which might possibly be related to the Southern Oscillation.

The zonal component of the extended Eliassen-Palm (E-P) flux associated with the “seesaw” structures accounts for most of the very low frequency barotropic energy conversion from the time-mean flow. The PNA and EA patterns, which have “seesaws” located in the jet exit regions, obtain kinetic energy more efficiently than the other patterns. The time scale for replenishing their kinetic energy is 3–4 days. The EU pattern, which has no “seesaw” structure, exhibits the smallest kinetic energy conversion. The fact that the WA and WP patterns straddle the storm tracks suggests that they may have a special relationship to baroclinic wave activity.

Abstract

Special observations were made over the southwest island area of the East China Sea from 12 to 27 January 1991 as part of the World Climate Research Program in Japan (WENPEX—Western North Pacific Cloud–Radiation Experiment). Two aircraft were used to determine the air truth of the total vertical liquid water path (LWP) using a microwave radiometer. One airplane was fitted with a 37-GHz radiometer and flew above planetary boundary layer clouds. The other flew inside the clouds with a cloud droplet spectrometer. These aircraft flew simultaneously along the same flight path when planetary boundary layer clouds were formed over the warm sea during an outbreak of cold air.

The result of the air truth of the LWP_radiometer indicates that the 37-GHZ microwave radiometer gives an estimation of the LWP accurate to 100 mg cm⁻². The shortwave cloud albedo was related to the LWP_radiometer. The albedo increases with the LWP, independent of cloud type, when measured just above the cloud tops. The measured albedo is nearly the same as the calculated albedo when the LWP_radiometer is larger than 60 mg cm⁻² but much smaller than the calculated albedo when the LWP_radiometer is less than 40 mg cm⁻². Cloud-top irregularity is suggested to be the primary cause of this discrepancy. The degree of inhomogeneity of the horizontal distribution of liquid water appears to be correlated with the amount of precipitable water in the planetary boundary layer.

Abstract

In Order to observe stratospheric gravity waves and turbulence, a Gill-type anemometer was improved by using sapphire pivot bearings and photocouplter tachometers. The anemometer has a threshold velocity of less than 1 m s⁻¹ in the middle stratosphere, and the performance is very stable for mechanical shocks and temperature variations. The first observational flight of the anemometer was successfully carried out in September 1982. The most interesting result of this observation is that there often exist gust-like wind fluctuations of 1–3 m s⁻¹ in the stratosphere.

Abstract

Hurricane Gustav (2008) made landfall in southern Louisiana on 1 September 2008 with its eye never closer than 75 km to New Orleans, but its waves and storm surge threatened to flood the city. Easterly tropical-storm-strength winds impacted the region east of the Mississippi River for 12–15 h, allowing for early surge to develop up to 3.5 m there and enter the river and the city’s navigation canals. During landfall, winds shifted from easterly to southerly, resulting in late surge development and propagation over more than 70 km of marshes on the river’s west bank, over more than 40 km of Caernarvon marsh on the east bank, and into Lake Pontchartrain to the north. Wind waves with estimated significant heights of 15 m developed in the deep Gulf of Mexico but were reduced in size once they reached the continental shelf. The barrier islands further dissipated the waves, and locally generated seas existed behind these effective breaking zones.

The hardening and innovative deployment of gauges since Hurricane Katrina (2005) resulted in a wealth of measured data for Gustav. A total of 39 wind wave time histories, 362 water level time histories, and 82 high water marks were available to describe the event. Computational models—including a structured-mesh deepwater wave model (WAM) and a nearshore steady-state wave (STWAVE) model, as well as an unstructured-mesh “simulating waves nearshore” (SWAN) wave model and an advanced circulation (ADCIRC) model—resolve the region with unprecedented levels of detail, with an unstructured mesh spacing of 100–200 m in the wave-breaking zones and 20–50 m in the small-scale channels. Data-assimilated winds were applied using NOAA’s Hurricane Research Division Wind Analysis System (H*Wind) and Interactive Objective Kinematic Analysis (IOKA) procedures. Wave and surge computations from these models are validated comprehensively at the measurement locations ranging from the deep Gulf of Mexico and along the coast to the rivers and floodplains of southern Louisiana and are described and quantified within the context of the evolution of the storm.

Abstract

The complex interactions between water vapor fields and deep atmospheric convection remain one of the outstanding problems in tropical meteorology. The lack of high spatial–temporal resolution, all-weather observations in the tropics has hampered progress. Numerical models have difficulties, for example, in representing the shallow-to-deep convective transition and the diurnal cycle of precipitation. Global Navigation Satellite System (GNSS) meteorology, which provides all-weather, high-frequency (5 min), precipitable water vapor estimates, can help. The Amazon Dense GNSS Meteorological Network experiment, the first of its kind in the tropics, was created with the aim of examining water vapor and deep convection relationships at the mesoscale. This innovative, Brazilian-led international experiment consisted of two mesoscale (100 km × 100 km) networks: 1) a 1-yr (April 2011–April 2012) campaign (20 GNSS meteorological sites) in and around Manaus and 2) a 6-week (June 2011) intensive campaign (15 GNSS meteorological sites) in and around Belem, the latter in collaboration with the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (CHUVA) Project in Brazil. Results presented here from both networks focus on the diurnal cycle of precipitable water vapor associated with sea-breeze convection in Belem and seasonal and topographic influences in and around Manaus. Ultimately, these unique observations may serve to initialize, constrain, or validate precipitable water vapor in high-resolution models. These experiments also demonstrate that GNSS meteorology can expand into logistically difficult regions such as the Amazon. Other GNSS meteorology networks presently being constructed in the tropics are summarized.

Abstract

The NASA Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP²Ex) employed the NASA P-3, Stratton Park Engineering Company (SPEC) Learjet 35, and a host of satellites and surface sensors to characterize the coupling of aerosol processes, cloud physics, and atmospheric radiation within the Maritime Continent’s complex southwest monsoonal environment. Conducted in the late summer of 2019 from Luzon Philippines in conjunction with the Office of Naval Research Propagation of Intraseasonal Tropical OscillatioNs (PISTON) experiment with its R/V Sally Ride stationed in the North Western Tropical Pacific, CAMP²Ex documented diverse biomass burning, industrial and natural aerosol populations and their interactions with small to congestus convection. The 2019 season exhibited El Nino and associated drought, high biomass burning emissions, and an early monsoon transition allowing for observation of pristine to massively polluted environments as they advected through intricate diurnal mesoscale and radiative environments into the monsoonal trough. CAMP²Ex’s preliminary results indicate 1) increasing aerosol loadings tend to invigorate congestus convection in height and increase liquid water paths; 2) lidar, polarimetry, and geostationary Advanced Himawari Imager remote sensing sensors have skill in quantifying diverse aerosol and cloud properties and their interaction; and 3) high resolution remote sensing technologies are able to greatly improve our ability to evaluate the radiation budget in complex cloud systems. Through the development of innovative informatics technologies, CAMP²Ex provides a benchmark dataset of an environment of extremes for the study of aerosol, cloud and radiation processes as well as a crucible for the design of future observing systems.