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John A. Russo Jr.
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Edwin Kessler III and John A. Russo Jr.

Abstract

The great information-processing capacity of modern digital computers is used to assemble radar data in a form suitable for its application to weather analysis and forecasting studies and for investigation of the data's physical and statistical properties. Data are collected by PPI photography at steps of the antenna-elevation angle and radar-system sensitivity and aye reduced manually to digital form. The data are registered on magnetic tape for entry to the digital computer, wherein they are edited, range-normalized, reassembled to produce plan distributions that refer to a constant altitude above the earth, and processed for the distributions of the heights of echo bases and tops. Any of a practically limitless number of processing combinations can be selected to portray the intensity, male, and vertical development characteristic of the echoes for a particular period and location. The outputs of the computer program are printed distributions, for visual inspection and manual processing, and magnetic tapes containing the data in a form suitable for analysis by other computer routines. This program provides practical means for developing knowledge of radar data; realization of the full benefits of radar under operational conditions will require instruments which quantize the data rapidly.

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John A. Russo Jr., Isadore Enger, and Edna L. Sorenson

Abstract

The screening-multiple-regression technique is applied to predicting surface u- and v-wind components at Idlewild International Airport for periods of 2, 3, 5 and 7 hr. The predictors are variables from 11 synoptic stations, easily obtained or derivable from conventional service A teletype data. Additional predictors are used to account for diurnal and seasonal variations. In all, 141 predictors are screened and one prediction equation is obtained for each predictand. Each equation is applicable to any hour of the day and any day of the year.

The regression equations derived from a dependent sample selected randomly from 7 years of data proved significantly better at the 1-per cent level than both persistence and climatology for the 3-, 5- and 7-hr forecasts and at the 5 per cent level for the 2-hr forecasts when tested on 1387 independent cases. The screening-regression root-mean-square errors on this independent set ranged from 3.36 kt to 4.48 kt for the u-wind forecasts and from 3.69 kt to 5.57 kt for the v-wind forecasts.

Operational 3-, 5- and 7-hr surface-wind forecasts extracted from terminal forecasts made at Idlewild are compared both quantitatively and categorically with corresponding regression forecasts made on a new set of independent data. The screening-regression forecast errors are approximately ⅓ smaller than the subjective errors, and the improvements for all the predictands are statistically significant beyond the 1 per cent level. The categorical comparison concerning only categories of <10 kt and ≥10 kt (dictated by the format of the subjective data) resulted in Heidke skill scores of 0.399 for screening regression and 0.249 for the subjective forecasts when applied to 7-hr prediction of the surface-wind speed at Idlewild.

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A. Artegiani, E. Paschini, A. Russo, D. Bregant, F. Raicich, and N. Pinardi

Abstract

A comprehensive historical hydrographic dataset for the overall Adriatic Sea basin is analyzed in order to define the open ocean seasonal climatology of the basin. The authors also define the regional climatological seasons computing the average monthly values of heat fluxes and heat storage from a variety of atmospheric datasets. The long term mean surface heat balance corresponds to a heat loss of 19–22 W m−2. Thus, in steady state, the Adriatic should import about the same amount of heat from the northern Ionian Sea through the Otranto Channel. The freshwater balance of the Adriatic Sea is defined by computing the average monthly values of evaporation, precipitation, and river runoff, obtaining an annual average gain of 1.14 m. The distribution of heat marks the difference between eastern and western Adriatic areas, showing the winter heat losses in different parts of the basin.

Climatological water masses are defined for three regions of the Adriatic: (i) the northern Adriatic where seasonal variations in temperature penetrate to the bottom; deep water (NAdDW) with σ t > 29.2 kg m−3 is produced and salinity is greatly affected by river discharges; (ii) the middle Adriatic where a pool of modified NAdDW is stored during the summer season after being renewed in winter and modified Levantine Intermediate Water (MLIW) intrudes from the southern regions between spring and autumn; and (iii) the southern Adriatic where homogeneous water properties are found below 150 m (the local maximum depth of the seasonal thermocline) and a different deep water mass (SAdDW) is found with σ t > 29.1 kg m−3, T ≈ 13.5°C, and S ≈ 38.6 psu. Due to river runoff waters, the surface layers of all three regions are freshened during the spring–summer seasons. The vertical distributions of dissolved oxygen vary quantitatively in the three regions showing a spring–summer subsurface maximum due to the balance between phytoplankton growth in the euphotic zone and low vertical mixing in the water column. This behavior can be reconciled with open ocean conditions except for the northernmost part of the Adriatic where well-mixed oxygen conditions prevail throughout the year.

Large interannual anomalies of both temperature and salinity are found at the geographical center of the basin in surface and deep waters (100 m).

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A. Artegiani, E. Paschini, A. Russo, D. Bregant, F. Raicich, and N. Pinardi

Abstract

In the second part of the paper dedicated to the Adriatic Sea general circulation, the horizontal structure of the hydrographic parameters and dissolved oxygen fields is described on a seasonal timescale.

Maps of temperature and salinity climatological fields reveal the enhanced seasonal variability of the Adriatic Sea, which at the surface is associated with the major dilution effects of river runoff.

The density and derived dynamic height fields show for the first time the baroclinic geostrophic structure of the general circulation. Winter is dominated by compensation effects between temperature and salinity fronts along the western coastline. The resulting baroclinic circulation is weak and suggests the presence of barotropic current components not accessible by the dataset. Spring and summer seasons have the smallest spatial scales in the temperature and salinity fields and stronger subbasin-scale gyres and current systems, which have been classified in a schematic representation of the circulation. The Adriatic Sea general circulation comprises boundary currents and jets that strengthen and change spatial scales in different seasons. Two separate cyclonic gyres clearly exist in the middle and southern Adriatic except during winter.

The rates of formation of the northern Adriatic deep waters and southern Adriatic deep waters are estimated to be 0.07 and 0.36 Sv (Sv ≡ 106 m3 s−1), respectively. Likely driving mechanisms of the circulation are discussed.

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Charles Chemel, Maria R. Russo, John A. Pyle, Ranjeet S. Sokhi, and Cornelius Schiller

Abstract

The development of a severe Hector thunderstorm that formed over the Tiwi Islands, north of Australia, during the Aerosol and Chemical Transport in Tropical Convection/Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere (ACTIVE/SCOUT-O3) field campaign in late 2005, is simulated by the Advanced Research Weather Research and Forecasting (ARW) model and the Met Office Unified Model (UM). The general aim of this paper is to investigate the role of isolated deep convection over the tropics in regulating the water content in the upper troposphere/lower stratosphere (UT/LS). Using a horizontal resolution as fine as 1 km, the numerical simulations reproduce the timing, structure, and strength of Hector fairly well when compared with field campaign observations. The sensitivity of results from ARW to horizontal resolution is investigated by running the model in a large-eddy simulation mode with a horizontal resolution of 250 m. While refining the horizontal resolution to 250 m leads to a better representation of convection with respect to rainfall, the characteristics of the Hector thunderstorm are basically similar in space and time to those obtained in the 1-km-horizontal-resolution simulations. Several overshooting updrafts penetrating the tropopause are produced in the simulations during the mature stage of Hector. The penetration of rising towering cumulus clouds into the LS maintains the entrainment of air at the interface between the UT and the LS. Vertical exchanges resulting from this entrainment process have a significant impact on the redistribution of atmospheric constituents within the UT/LS region at the scale of the islands. In particular, a large amount of water is injected in the LS. The fate of the ice particles as Hector develops drives the water vapor mixing ratio to saturation by sublimation of the injected ice particles, moistening the air in the LS. The moistening was found to be fairly significant above 380 K and averaged about 0.06 ppmv in the range 380–420 K for ARW. As for UM, the moistening was found to be much larger (about 2.24 ppmv in the range of 380–420 K) than for ARW. This result confirms that convective transport can play an important role in regulating the water vapor mixing ratio in the LS.

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