Synoptic/planetary-scale interactions and blocking over the North Atlantic Ocean

The work completed under this grant represents a continuing investigation of synoptic/planetary-scale interactions over the North Atlantic Ocean in late Jan. 1979. The focus of attention was a blocking episode that developed over southern Greenland on 21 Jan. However, the diagnosis also extended to antecedent cyclone activity and the role of moist processes during wave development. In all, the project was partitioned into two phases: (1) an extension of diagnoses that were already in progress of the 21 Jan. blocking episode and its antecedent cyclone activity using satellite-enhanced level 3-b NASA/Goddard Laboratory for Atmospheres (GLA) analyses; and (2) an analysis of the extent to which the results of Phase 1 are sensitive to the presence of satellite information

Synoptic/planetary-scale interactions and blocking over the North Atlantic Ocean

The focus was on the development of a blocking anticyclone that formed over the North Atlantic in January 1979 and a marine cyclone that deepened explosively prior to the onset of the block. The extended height tendency equation was used as the primary diagnostic tool. Focusing on the domain encompassing the migrating ridge that eventually formed the block, it was found that vorticity advection played the dominant role in the development of the ridge and the formation of the block. Also of interest was an attempt to evaluate the relative importance of synoptic-scale, planetary-scale, and synoptic/planetary-scale interactions as the block developed. To accomplish this, all data fields were partitioned into synoptic and planetary-scale components using a Barnes-type filter. Finally, the cyclone was diagnosed by examining the low level static stability fields associated with the cyclone's development

Planetary and synoptic-scale interactions during the life cycle of a mid-latitude blocking anticyclone over the North Atlantic

The formation of a blocking anticyclone over the North Atlantic has been examined over its entire life-CyCle using the Zwack-Okossi (Z-O) equation as the diagnostic tool. This blocking anticyclone occurred in late October and early November of 1985. The data used were provided by the NASA Goddard Laboratory for Atmospheres on a global 2.O degree latitude by 2.5 degree longitudinal grid. The horizontal distribution of the atmospheric forcing mechanisms that were important to 500 mb block formation, maintenance and decay were examined. A scale-partitioned form of the Z-O equation was then used to examine the relative importance of forcing on the planetary and synoptic scales, and their interactions. As seen in previous studies, the results presented here show that upper tropospheric anticyclonic vorticity advection was the most important contributor to block formation and maintenance. However, adiabatic warming, and vorticity tilting were also important at various times during the block lifetime. In association with precursor surface cyclogenesis, the 300 mb jet streak in the downstream (upstream) from a long-wave trough (ridge) amplified significantly. This strengthening of the jet streak enhanced the anti-cyclonic vorticity advection field that aided the amplification of a 500 mb short-wave ridge. Tile partitioned height tendency results demonstrate that the interactions between the planetary and sn,noptic-scale through vorticity advection was the most important contributor to block formation. Planetary-scale, synoptic-scale. and their interactions contributed weakly to the maintenance of the blocking anticyclone with the advection of synoptic-scale vorticity by the planetary-scale flow playing a more important role. Planetary-scale decay ofthe long-wave ridge contributed to the demise of this blocking event

Study of the effect of cloud inhomogeneity on the earth radiation budget experiment

The Earth Radiation Budget Experiment (ERBE) is the most recent and probably the most intensive mission designed to gather precise measurements of the Earth's radiation components. The data obtained from ERBE is of great importance for future climatological studies. A statistical study reveals that the ERBE scanner data are highly correlated and that instantaneous measurements corresponding to neighboring pixels contain almost the same information. Analyzing only a fraction of the data set when sampling is suggested and applications of this strategy are given in the calculation of the albedo of the Earth and of the cloud-forcing over ocean

The Life Cycles of Intense Cyclonic and Anticyclonic Circulation Systems Observed over Oceans

This report presents a summary of research accomplished over the past four years under the sponsorship of NASA grant #NAG8-915. Building on previously funded NASA grants, this part of the project focused on the following specific goals relative to cyclone/anticyclone systems: the jet streak link between block formation and upstream cyclone activity; the role of northward warm air advection in block formation; the importance of cooperative participation of several forcing mechanisms during explosive cyclone development; and the significance of the vertical distribution of forcing processes during cyclone/anticyclone development

The life cycles of intense cyclonic and anticyclonic circulation systems observed over oceans

Full attention was now directed to the blocking case studies mentioned in previous reports. Coding and initial computational tests were completed for a North Atlantic blocking case that occurred in late October/early November 1985 and an upstream cyclone that developed rapidly 24 hours before block onset. This work is the subject of two papers accepted for presentation at the International Symposium on the Lifecycles of Extratropical Cyclones in Bergen, Norway, 27 June - 1 July 1994. This effort is currently highlighted by two features. The first is the extension of the Zwack-Okossi equation, originally formulated for the diagnosis of surface wave development, for application at any pressure level. The second is the separation of the basic large-scale analysis fields into synoptic-scale and planetary-scale components, using a two-dimensional Shapiro filter, and the corresponding partitioning of the Zwack-Okossi equation into synoptic-scale, planetary-scale, and synoptic/planetary-scale interaction terms. Preliminary tests suggest substantial contribution from the synoptic-scale and interaction terms

Synoptic/planetary-scale interactions and blocking over the North Atlantic Ocean

The central theme of this project has been the diagnosis of blocking anticyclogenesis and the corresponding interactions with synoptic-scale circulations. To that end an extensive investigation of the dynamics and energetics of a major blocking anticyclone and two upstream cyclones, all of which occurred over the North Atlantic Ocean and the United States in January 1979, was undertaken. Data for the study were provided by Goddard Laboratory for Atmospheres (GLA) 4 LAT by 5 LON FGGE analyses. The methodology has primarily focused on the diagnosis of circulation forcing mechanisms using the modified forms (referred to as the extended forms) of the height tendency and Zwack-Okossi equations developed by our research group. Calculations use routine second-order finite differencing with boundary layer fraction and sensible heating and latent heat release represented as parameterized quantities. Of particular interest are the latent heat release estimates, which combine convectional parameterized values with estimates derived from satellite IR data. The latter were obtained using an algorithm derived by Dr. Franklin R. Robertson of NASA's Marshall Space Flight Center. Results are contained in project reports, theses and publications identified in previous review summaries and reports, and publications listed at the end of this summary. Significant accomplishments in the past year are presented

Humpback and Fin Whaling in the Gulf of Maine from 1800 to 1918

The history of whaling in the Gulf of Maine was reviewed primarily to estimate removals of humpback whales, Megaptera novaeangliae, especially during the 19th century. In the decades from 1800 to 1860, whaling effort consisted of a few localized, small-scale, shore-based enterprises on the coast of Maine and Cape Cod, Mass. Provincetown and Nantucket schooners occasionally conducted short cruises for humpback whales in New England waters. With the development of bomb-lance technology at mid century, the ease of killing humpback whales and fin whales, Balaenoptera physalus, increased. As a result, by the 1870’s there was considerable local interest in hunting rorquals (baleen whales in the family Balaenopteridae, which include the humpback and fin whales) in the Gulf of Maine. A few schooners were specially outfitted to take rorquals in the late 1870’s and 1880’s although their combined annual take was probably no more than a few tens of whales. Also in about 1880, fishing steamers began to be used to hunt whales in the Gulf of Maine. This steamer fishery grew to include about five vessels regularly engaged in whaling by the mid 1880’s but dwindled to only one vessel by the end of the decade. Fin whales constituted at least half of the catch, which exceeded 100 animals in some years. In the late 1880’s and thereafter, few whales were taken by whaling vessels in the Gulf of Maine

The Interactions between a Midlatitude Blocking Anticyclone and Synoptic-Scale Cyclones That Occurred during the Summer Season

Using the Goddard Laboratory for Atmospheres Goddard Earth Observing System 5-yr analysis and the Zwack-Okossi equation as the diagnostic tool, the horizontal distribution of the dynamic and thermodynamic forcing processes contributing to the maintenance of a Northern Hemisphere midlatitude blocking anticyclone that occurred during the summer season were examined. During the development of this blocking anticyclone, vorticity advection, supported by temperature advection, forced 500-hPa height rises at the block center. Vorticity advection and vorticity tilting were also consistent contributors to height rises during the entire life cycle. Boundary layer friction, vertical advection of vorticity, and ageostrophic vorticity tendencies (during decay) consistently opposed block development. Additionally, an analysis of this blocking event also showed that upstream precursor surface cyclones were not only important in block development but in block maintenance as well. In partitioning the basic data fields into their planetary-scale (P) and synoptic-scale (S) components, 500-hPa height tendencies forced by processes on each scale, as well as by interactions (I) between each scale, were also calculated. Over the lifetime of this blocking event, the S and P processes were most prominent in the blocked region. During the formation of this block, the I component was the largest and most consistent contributor to height rises at the center point. It was also shown that the height- rise regions located on the anticyclonic side of the jet maxima associated with block development and intensification were primarily composed of the S and I components. Also, the precursor cyclones were associated with S or S and I height rises that contributed to the formation of this block. Finally, the results of this paper show that the forcing associated with summer-season blocking events are similar to that of their winter-season counterparts neglecting the natural case-to-case variability. In comparing these results to the results of other papers in this series, however, it is suggested that there may be two models for block development