An integrated forecasting and data assimilation system has been and is continuing to be developed by the Meteorological Research Branch (MRB) in partnership with the Canadian Meteorological Centre (CMC) of Environment Canada. Part I of this two-part paper motivates the development of the new system, summarizes various considerations taken into its design, and describes its main characteristics.

https://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281998%29126%3C1373%3ATOCMGE%3E2.0.CO%3B2

The Operational CMC–MRB Global Environmental Multiscale (GEM) Model. Part I: Design Considerations and Formulation

Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year–1) and weaker tropical emission of +0.1 Pg C year–1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year–1, respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.

https://science.sciencemag.org/content/sci/316/5832/1732.full.pdf

Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2

[1] Meteorological observations, in situ data, and satellite images of dust episodes were used already in the 1970s to estimate that 100 Tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and are deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but it deteriorates air quality, as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport, and deposition. The Terra spacecraft, launched at the dawn of the last millennium, provides the first systematic well-calibrated multispectral measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and to evaluate the African dust column concentration, transport, and deposition. We found that 240 ± 80 Tg of dust are transported annually from Africa to the Atlantic Ocean, 140 ± 40 Tg are deposited in the Atlantic Ocean, 50 Tg fertilize the Amazon Basin (four times as previous estimates, thus explaining a paradox regarding the source of nutrition to the Amazon forest), 50 Tg reach the Caribbean, and 20 Tg return to Africa and Europe. The results are compared favorably with dust transport models for maximum particle diameter between 6 and 12 μm. This study is a first example of quantitative use of MODIS aerosol for a geophysical research.

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Dust transport and deposition observed from the Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic Ocean

Global distribution of aeolian dust is simulated from 1981 to 1996 with the Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. The results are compared with in situ measurements and satellite data. An index is calculated from the model results and the satellite viewing angles to allow quantitative comparison with the Total ozone mapping spectrometer (TOMS) absorbing aerosol index. The annual budget over the different continents and oceans are analyzed. The simulated annual emission varies from a minimum of 1950 Tg in 1996 to a maximum of 2400 Tg in 1988. Of these emissions, 65% is from North Africa and 25% from Asia. It is found that North America received twice as much dust from other continents than it emits per year. There is no significant trend over the 16-year simulation. The inter-annual variability of dust distribution is analyzed over the North Atlantic and Africa. It is found that in winter a large fraction of the North Atlantic and Africa dust loading is correlated with the North Atlantic Oscillation (NAO) index. It is shown that a controlling factor of such correlation can be attributed to dust emission from the Sahel. The Bodele depression is the major dust source in winter and its inter-annual variability is highly correlated with the NAO. However, the long record of dust concentration measured at Barbados indicates that there is no correlation with the NAO index and surface concentration in winter. Longer simulation should provide the information needed to understand if the effects of the NAO on dust distribution is rather limited or Barbados is at the edge of the affected region.  2003 Elsevier Ltd. All rights reserved.

/pdf/long-term-simulation-of-global-dust-distribution-with-the-2ztupse5ua.pdf

Long-term simulation of global dust distribution with the GOCART model : correlation with North Atlantic Oscillation

The Eastern Mediterranean and the Middle East (EMME) are likely to be greatly affected by climate change, associated with increases in the frequency and intensity of droughts and hot weather conditions. Since the region is diverse and extreme climate conditions already common, the impacts will be disproportional. We have analyzed long-term meteorological datasets along with regional climate model projections for the 21st century, based on the intermediate IPCC SRES scenario A1B. This suggests a continual, gradual and relatively strong warming of about 3.5–7°C between the 1961–1990 reference period and the period 2070–2099. Daytime maximum temperatures appear to increase most rapidly in the northern part of the region, i.e. the Balkan Peninsula and Turkey. Hot summer conditions that rarely occurred in the reference period may become the norm by the middle and the end of the 21st century. Projected precipitation changes are quite variable. Annual precipitation is expected to decrease in the southern Europe – Turkey region and the Levant, whereas in the Arabian Gulf area it may increase. In the former region rainfall is actually expected to increase in winter, while decreasing in spring and summer, with a substantial increase of the number of days without rainfall. Anticipated regional impacts of climate change include heat stress, associated with poor air quality in the urban environment, and increasing scarcity of fresh water in the Levant.

/pdf/climate-change-and-impacts-in-the-eastern-mediterranean-and-51v3tunbgb.pdf

Climate change and impacts in the Eastern Mediterranean and the Middle East.

An investigation of the main features of large-scale synoptic patterns over Europe and the adjacent areas for extreme winter periods during 1980–1995 over the Eastern Mediterranean (EM) is performed. The NASA reanalysis data set is used to investigate composite sea level pressure (SLP), geopotential height of the 500 hPa surface (H-500) and precipitation–wet, normal and dry patterns for each month during the period October–March. It is found that the wet and dry cool seasons in the EM are associated with distinct SLP and H-500 anomaly patterns over Europe and the adjacent regions. During the dry spells large-scale positive SLP/H-500 anomaly areas prevail over Eastern Europe. A negative SLP anomaly is normally found during these periods over southwestern and Western Europe. During the wet cool seasons in the EM there are mainly negative SLP/H-500 anomaly areas over Eastern Europe to the north east of the EM. Positive SLP/H-500 anomalies are found over Western Europe. During wet months a trough zone between the Siberian and the Azorean Highs is positioned over the eastern part of the Mediterranean. During dry months the Siberian anticyclone is more intensive and the zone with low surface pressure is displaced to the central part of the northern Mediterranean.

Monthly Synoptic Patterns Associated with Wet/Dry Conditions in the Eastern Mediterranean

A dust prediction system, developed earlier at the University of Athens within the framework of the Mediterranean Dust Experiment (MEDUSE) project, was enhanced at Tel Aviv University to support the Israeli–American Mediterranean Israeli Dust Experiment (MEIDEX) project. These enhancements include development of a dust initialization approach using Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) data and improved specification of the dust sources. The skill of the model against the TOMS AI measurements was tested during two periods in March and June 2000 using four different scores. It is shown that the TOMS-based initialization has a significant positive impact on all the scores. For instance, the average distance between the predicted and TOMS-observed dust plumes drops from 350–485 to less than 200 km. Verification of model forecasts against surface dust measurements in Tel Aviv shows correlations of up to 0.69 based on 27 predictions, for both 24 and 48 h. One example of a narrow d...

A Dust Prediction System with TOMS Initialization

The roles of topography, convection, sensible and latent heat fluxes in Alpine lee cyclogenesis are investigated. The adoption of a newly developed factor separation method allows the identification of the contributions of each of these processes as well as their synergistic effects. Topographical blocking is the dominant factor in the first and most rapid phase of the cyclone deepening. This is followed by the convection contribution at the 2nd but slower phase. Local moisture flux is dominant in the 3rd phase accompanied by a significant cyclolytic contribution by the Alps. Between the 1st and the 2nd phases of deepening, the synergistic effect of convection induced by the mountains plays an important role in the deepening at a time when the convection independent of mountains has not become yet so active. Coarser horizontal resolutions still capture these features, although to a lesser extent. Model simulation results are shown to be strongly dependent upon the chosen set of factors. As the number of factors increases, a specific contribution diminishes because synergistic terms with the new factors are extracted from the contribution of the specific factor under investigation. Another interesting conclusion is that the elimination of an important factor from the investigation will not remove its contribution. It will reappear and be attributed to another factor which is the most synergistic to the important factor. The spread of the cyclones' centers in the model simulations is shown to be a powerful tool in understanding the effects of different factors on the evolution of the model solutions. For instance, convection moves the cyclone to the east northeast while topography ties the cyclone to the lee of the Alps. The sea moisture fluxes tend to move the cyclone toward the warm bodies of water. DOI: 10.1034/j.1600-0870.1996.t01-1-00002.x

A multi-stage evolution of an ALPEX cyclone

The contribution of a particular process is shown to be strongly dependent upon the other processes under investigation because of synergistic contributions. In general, as the number of relevant factors being investigated increases, the role of any specific factor diminishes because the synergistic interactions with the new factors are extracted. This is illustrated with the variations of the topographic role in the impressive lee cyclone deepening event on 3–5 March 1982 during the Alpine Experiment. When latent heat release, latent heat flux, and sensitive heat flux enter into our comparative study, the topographic contribution to the surface pressure lee cyclone deepening gradually diminishes down to 50% or more.

M. Tsidulko

Papers

Monthly Synoptic Patterns Associated with Wet/Dry Conditions in the Eastern Mediterranean

A Dust Prediction System with TOMS Initialization

A multi-stage evolution of an ALPEX cyclone

Can Sensitivity Studies Yield Absolute Comparisons for the Effects of Several Processes

November 2, 1994, severe storms in the southeastern Mediterranean