Thickness Anomalies Research Articles

Interannual variability in the onset of the summer monsoon over the Eastern Bay of Bengal

Climatological characteristics associated with summer monsoon onset over the eastern Bay of Bengal (BOB) are examined in terms of the westerly-easterly boundary surface (WEB). The vertical tilt of the WEB depends on the horizontal meridional temperature gradient (MTG) near the WEB, under the constraint of the thermal wind balance. The switch in the WEB tilt firstly occurs between 90 and 100°E during the first pentad of May. At this time the 850 hPa ridgeline splits over the BOB and heavy rainfall commences over the eastern BOB, indicating the onset of the BOB summer monsoon (BOBSM). The area-averaged MTG (200–500 hPa) is proposed as an index to define the BOBSM onset. A comparison of the onset determined by the MTG, 850 hPa zonal wind, and outgoing longwave radiation (OLR) shows that the MTG index is the most effective in characterizing the interannual variability of the BOBSM onset. Strong precursor signals are found prior to an anomalous BOBSM onset. Composite results show that early (late) BOBSM onset follows excessive (deficient) rainfall over the western Pacific and anomalous lower tropospheric cyclonic circulation which extends zonally from the northern Indian Ocean into the western Pacific, and strong (weak) equatorial westerly anomalies in the preceding winter and spring. Prior to an early (late) BOBSM onset, significant positive (negative) thickness anomalies exist around the Tibetan Plateau, accompanied by anomalous upper tropospheric anticyclonic (cyclonic) circulation. The interannual variations of the BOBSM onset are significantly correlated with anomalous sea surface temperature related to ENSO. These occurs through changes in the Walker circulation and local Hadley circulation, leading to middle and upper tropospheric temperature anomalies over the Asian sector. The strong precursor signals around the Tibetan Plateau may be partly caused by local snow cover anomalies, and an early (late) BOBSM onset is preceded by less (more) snow accumulation over the Tibetan Plateau during the preceding winter.

Variability of Fram Strait sea ice export: causes, impacts and feedbacks in a coupled climate model

Analyses of a 500-year control integration of the global coupled atmosphere–sea ice–ocean model ECHAM5.0/MPI-OM show a high variability in the ice export through Fram Strait on interannual to decadal timescales. This variability is mainly determined by variations in the sea level pressure gradient across Fram Strait and thus geostrophic wind stress. Ice thickness anomalies, formed at the Siberian coast and in the Chukchi Sea, propagate across the Arctic to Fram Strait and contribute to the variability of the ice export on a timescale of about 9 years. Large anomalies of the ice export through Fram Strait cause fresh water signals, which reach the Labrador Sea after 1–2 years and lead to significant changes in the deep convection. The associated anomalies in ice cover and ocean heat release have a significant impact on air temperature in the Labrador Sea and on the large-scale atmospheric circulation. This affects the sea ice transport and distribution in the Arctic again. Sensitivity studies, simulating the effect of large ice exports through Fram Strait, show that the isolated effect of a prescribed ice/fresh water anomaly is very important for the climate variability in the Labrador Sea. Thus, the ice export through Fram Strait can be used for predictability of Labrador Sea climate up to 2 years in advance.

A subway map for the lungs: Planar occlusion-free visualization of the bronchial tree

High resolution CT datasets from multi-slice scanners allow the inspection of thetracheobronchial tree down to the smaller airways for diagnostic purposes (e.g. to inspectairway lumen and bronchial wall thickness). Using manual or automated segmentationmethods, the bronchial tree structure may be discernable down to hundreds of subsegmentsof higher generations. Linear projections (such as maximum intensity projections) of thedelicate three-dimensional tree lead to multiple occlusions (left figure), and make theinspection and navigation along specific airway paths cumbersome.The planar mapping is computed automatically for each automatically extractedindividual bronchial tree. It gives an overview of the bronchial tree in a single glance, isprintable (e.g. for the diagnostic report), allows to convey diagnostic CAD-information tothe reader through color-coding (e.g. anomalies in wall thickness or broncho-arterialdiameter ratios), and eases three-dimensional navigation through the bronchial tree (themap is bijectively linked to the 3D image volume).The suggested mapping is also applicable to show anomalies in the pulmonary arterialtree.Two possible approaches for automatic production of a non-intersecting topological mapping:multi-slice CT lung segmentation airway tree segmentation centerline extractionThe topological mapping (subway map) can aid the navigationthrough the bronchial tree. A mouse-click into the subway map willset the ortho-viewer to the corresponding true 3D-position, indicatethe position in the three-dimensional tree model, and show areformat of the selected airway location which is reformattedperpendicular to the local airway orientation .(a) At each bifurcation of generation i, the mappingbranches by an angle ± θ

Synoptic-Scale Precursors to Significant Cold-Season Precipitation Events in Burlington, Vermont

Abstract Several classes of significant cold-season precipitation events occurring in Burlington, Vermont (KBTV), during the 33-yr period from 1963 to 1995, are studied with the objective of identifying large-scale circulation precursors to the more extreme events. Several physically interesting and unique features that correspond to 24-h totals of 25 to 50 mm of precipitation are found. Preferential southerly and more maritime surface geostrophic flow occur in the heavier cases, in association with a strong cyclone (anticyclone) to the west (east) of KBTV. The 1000–500-hPa positive thickness anomaly corresponds to a depth-mean virtual temperature anomaly of +10.5°C in the heavy events. Additionally, statistically significant negative thickness anomalies, responsible for triggering these significant precipitation events, can be traced westward to a position in the Pacific Ocean at least 6 days prior to the event. Significantly heavier precipitable water amounts and preferentially strong water vapor transp...

Temporal and spatial variation of shore-fast ice in the Kara Sea

The present study of temporal and spatial variations of shore-fast ice in the Kara Sea includes utilization of aircraft observations by the Arctic and Antarctic Research Institute (AARI) from 1953 to 1990, and surface brightness temperature from SSM/I from 1987 to 2001. Analyses of a time series of spatially distributed SSM/I brightness temperatures provide estimates of the shore-fast ice extent. The present work shows spatial distributions of frequencies of shore-fast ice coverage in the Kara Sea for each month, and it gives a time series of its area. The fast ice extent in early spring typically reaches a stable configuration, which falls into one of two different categories (modes) with significantly different area. The smaller of these two modes tends to appear with increased frequency since 1980. This gives, for this period, a negative trend in fast ice area during spring. There is a correlation above 0.5 between the average winter temperature and maximum ice thickness anomalies and fast ice area. Analysis of surface wind data and sea level pressure indicates that wind during winter controls much of the shore-fast ice development. Specially strong westerly and southwesterly winds tend to give a smaller fast ice extent than otherwise. Variations in river discharge tend only to have an observable effect on the ice at the river mouths.

Late‐summer sea ice thickness variability in the Arctic Transpolar Drift 1991–2001 derived from ground‐based electromagnetic sounding

Late‐summer thickness distributions of large ice floes in the Transpolar Drift between Svalbard and the North Pole in 1991, 1996, 1998, and 2001 are compared. They have been derived from drilling and electromagnetic (EM) sounding. Results show a strong interannual variability, with significantly reduced thickness in 1998 and 2001. The mean thickness decreased by 22.5% from 3.11 m in 1991 to 2.41 m in 2001, and the modal thickness by 22% from 2.50 m in 1991 to 1.95 m in 2001. Since modal thickness represents the thickness of level ice, the observed thinning reflects changes in thermodynamic conditions. Together with additional data from the Laptev Sea obtained in 1993, 1995, and 1996, results are in surprising agreement with recently published thickness anomalies retrieved from satellite radar altimetry for Arctic regions south of 81.5°N. This points to a strong sensitivity of radar altimetry data to level ice thickness.

Formation and propagation of great salinity anomalies

North Atlantic/Arctic ocean and sea ice variability for the period 1948–2001 is studied using a global Ocean General Circulation Model coupled to a dynamic/thermodynamic sea ice model forced by daily NCEP/NCAR reanalysis data [Kalnay et al., 1996]. Variability of Arctic sea ice properties is analysed, in particular the formation and propagation of sea ice thickness anomalies that are communicated via Fram Strait into the North Atlantic. These export events led to the Great Salinity Anomalies (GSA) of the 1970s, 1980s and 1990s in the Labrador Sea (LS). All GSAs were found to be remotely excited in the Arctic, rather than by local atmospheric forcing over the LS. Sea ice and fresh water exports through the Canadian Archipelago (CAA) are found to be only of minor importance, except for the 1990s GSA. Part of the anomalies are tracked to the Newfoundland Basin, where they enter the North Atlantic Current. The experiments indicate only a minor impact of a single GSA event on the strength of the North Atlantic Thermohaline Circulation (THC).

Sea level changes in the North Atlantic by solar forcing and internal variability

Sea level change due to variations in the thermohaline structure of the North Atlantic has been calculated using a coupled ocean–atmosphere model of intermediate complexity (ECBilt). Two 1000-year simulations are made, one using a constant solar forcing and one using an estimate of historic variations in solar activity. In the solar forced simulation sea level variations are a proxy for climate variations. Anomalies in sea surface temperature (SST) of the northern North Atlantic are generated by the solar radiation changes. These SST anomalies modulate the ocean thermohaline circulation (THC), affecting surface salinities in the northern North Atlantic which are subsequently advected to the deep ocean. The associated deep ocean geopotential thickness anomalies dominate sea level in the North Atlantic and are advected southwards with the overturning circulation. Sea level change in the solar forced simulation is primarily an indirect response to solar radiation changes, which modulate the THC. In the unforced run, changes in the THC affect sea level in a similar way. However, in this simulation THC variability is no longer generated by sea surface temperature variations but by sea surface salinity variations, resulting from internal climate dynamics. The present results will aid in analyses of reconstructed low-frequency sea-level variations based on proxy data.

Interannual Variability in the Eastern Subtropical North Pacific Ocean

Abstract Interannual variability in the eastern subtropical North Pacific Ocean is investigated using the Naval Research Laboratory Layered Ocean Model (NLOM). Emphasis is placed on examining the nature of westward propagating Rossby waves and their interaction with the overlying atmosphere. Singular value decomposition (SVD), complex empirical orthogonal function (CEOF), and multichannel singular spectrum (M-SSA) analyses are used to isolate the standing and propagating response due to modeled Rossby waves and observed wind stress curl (WSC) anomalies as well as their dominant frequencies of oscillation, respectively. In addition to a large-scale interdecadal fluctuation, two distinct forms of Rossby waves are found to exist, one wind forced and the other freely propagating. SVD and CEOF analyses of NLOM upper layer thickness anomalies suggest a leading order source of variability stemming from a large-scale interdecadal fluctuation. M-SSA analysis also depicts this low frequency mode, but to a lesser ex...

Reykjanes "V"-shaped ridges originating from a pulsing and dehydrating mantle plume.

Prominent crustal lineations straddle the Reykjanes ridge, south of Iceland (Fig. 1). These giant V-shaped features are thought to record temporal variations in magma production at the Reykjanes ridge axis, associated with along-axis flow of Icelandic plume material. It has been proposed that this flow is channelled preferentially along the ridge axis, and that temporal variability is induced by fluctuations of the Iceland plume itself or, alternatively, by relocations of the ridge axis on Iceland. Here I present a geodynamic model that predicts the formation of crustal V-shaped ridges from a pulsing and radially flowing mantle plume. In this model, plume pulses produce mantle temperature perturbations that expand away from the plume in all directions beneath the zone of partial melting. The melting zone has a high viscosity owing to mantle dehydration at the onset of partial melting. This high-viscosity region allows for reasonable variations in crustal thickness, produces crustal Vs that extend hundreds of kilometres along the axis, and prevents the plume material from being preferentially channelled along the ridge axis. The angle of the crustal V-shaped features relative to the ridge axis reflects the rate of lateral plume flow, which remains several times greater than the ridge half-spreading rate over the length of a crustal V. Consequently, this radially expanding plume produces lineations in crustal thickness and free-air gravity anomalies that appear to be nearly straight.

Investigating the variability of the Arctic sea ice thickness in response to a stochastic thermodynamic atmospheric forcing

The natural low frequency variability of the sea-ice thickness in the Arctic is investigated based on a 10 000 years simulation with a one-dimensional thermodynamic sea-ice model forced by random perturbations of the air surface temperature and solar radiation. The simulation results suggest that atmospheric random perturbations are integrated by the sea-ice. Moreover those perturbations occurring at the onset of ice melting force the largest ice thickness anomalies, which are successively amplified in summer by the albedo feedback and damped in winter by the feedback of the heat conduction through the ice. They also result in a global shift of the melting season which, in the mean annual cycle, leads to earlier melting as compared to the mean climatological cycle. The power spectrum of the ice anomalies suggests that the thickness of the perennial ice should vary preferentially on a time scale of approximately 20 years. The shape of the spectrum is consistent with that of a first order Markov process in which the characteristic time scale of the ice fluctuations would be the relaxation time scale associated with the linear feedback. The equivalent Markov model is constructed by linearizing the ice growth rate anomaly equations and allows us to derive an analytical expression of the feedback and of the forcing of the anomalies. The characteristic time scale depends explicitly on those model parameters involved in the atmosphere-ice interaction but also on the mean seasonal characteristics of the forcing and of the ice thickness.

A Study of Temperature Changes in the Upper North Atlantic: 1950–94

In this paper, decadal evolution of warm and cold anomalies in the subtropical and subpolar gyres of the North Atlantic in the 300‐500-m and 100‐250-m depth ranges is described. A series of pentadally averaged objective maps of upper-ocean thermal anomalies, from bathythermograph data, are presented. Warm and cold anomalies in the western subtropical gyre are succeeded by similar anomalies in the subpolar gyre and the east Atlantic and subtropical return flow. Major warm and cold anomalies in the 1950s and 1970s, respectively, are similar to those described previously in SSTs, although there is more temporal continuity in the subsurface anomalies. Two very strong events in the subtropical gyre are identified, a cold anomaly in 1966‐72 and an intense warm anomaly in 1988‐94, that show the greatest temperature anomalies in the North Atlantic during the period of the study. Interisotherm thickness anomalies are shown for the subtropical gyre during these periods. In the warm period, mode waters are both warmer (188‐198C) and of greater volume than on average, and lie in a narrow band south of the Gulf Stream above a depressed thermocline with warm temperature anomalies to at least 800-m depth. In the cold period, the predominant mode water temperature is closer to 178C, but there is reduced water formation overall with a raised thermocline and cold temperature anomalies down to 600-m depth. The bowl of the gyre is flat during the cold period, and the implied recirculation may be weaker and extend farther to the south. The changes appear to be consistent with the intensification of the subtropical gyre in the warm period and a spindown in the cold period, although the relative roles of wind stress and air‐sea heat fluxes in these changes need to be determined.

A model study on internally generated variability in subtropical mode water formation

Internally generated variability in the subtropical gyre is studied as a possible mechanism for the observed interannual to decadal variability in subtropical mode water formation. An isopycnic ocean model with idealized geometry and forcing which mimics the North Atlantic subtropical gyre is used for this purpose. The horizontal resolution is sufficiently high and the friction and diffusion sufficiently low for the flow to become barotropically and baroclinically unstable. Two modes of low‐frequency variability are found. Both modes consist of westward propagating thickness anomalies. The anomalies have a first baroclinic modal structure with a maximum amplitude at the thermocline. One mode has a timescale of 8 years and a basin wide spatial scale; the other has a timescale of 4.5 years and a smaller spatial scale. The modes appear to be damped when the diffusion is high. In that case, the 8‐year mode can be excited by a spatially coherent stochastic wind stress. The evolution of the modes is determined by an interaction between the mean flow and the low‐frequency variability itself. The modes are instabilities of the mean flow determined by the basic stratification. It appears that coupling to the atmosphere and a parameterization of surface mixing are necessary for the low‐frequency variability to appear in the mixed layer. The coupling and surface mixing do not play a role in generating the modes. It is concluded that these internally generated modes may play a role in the observed variability in mode water formation.

Constructing Site-Specific Climate Change Scenarios on a Monthly Scale Using Statistical Downscaling

Monthly mean temperature and monthly precipitation totals in two small catchments in the Czech Republic are estimated from large-scale 500 hPa height and 1000/500 hPa thickness fields using statistical downscaling. The method used is multiple linear regression. Whereas precipitation can be determined from large-scale fields with some confidence in only a few months of the year, temperature can be determined successfully. Principal components calculated separately from the height and thickness anomalies are identified as the best predictor set. The method is most accurate if the regression is performed using seasons based on three months. The test on an independent sample, consisting of warm seasons, confirms that the method successfully reproduces the difference in mean temperature between two climatic states, which indicates that this downscaling method is applicable for constructing scenarios of a future climate change. The ECHAM3 GCM is used for scenario construction. The GCM is shown to simulate surface temperature and precipitation with low accuracy, whereas the large-scale atmospheric fields are reproduced well; this justifies the downscaling approach. The observed regression equations are applied to 2xCO2 GCM output so that the model’s bias is eleminated. This procedure is then discussed and finally, temperature scenarios for the 2xCO2 climate are constructed for the two catchments.

Atmospheric and surface variations during westerly wind bursts in the tropical western pacific

AbstractAn analysis is made of variations in both the surface energy balance and the regional atmospheric dynamic and thermal structure during 44 westerly wind bursts (WWBs) in the western equatorial Pacific Ocean from 1979 to 1995. The study assesses winds, convective available potential energy, cloud properties, precipitation, surface temperature, and surface heat flux while distinguishing between brief (5–25 day periodicity) and sustained (30–90 day) WWBs. Datasets used in the study include fields from the NCEP/NCAR and ECMWF re‐analyses, and satellite retrievals of clouds (ISCPP), precipitation (MSU), moisture (TOVS), and surface solar flux.Both brief and sustained WWBs, by definition, experience strong low‐level westerly winds that typically induce an increased surface latent‐heat flux of approximately 30 W m−2. Enhanced cloud thickness, precipitation, and upper tropospheric easterly wind anomalies accompany surface westerly winds, though maxima in winds lag those in clouds and precipitation by about one day for brief WWBs and four days for sustained events. WWBs of both types experience strong seasonality, occurring frequently in all seasons except boreal summer.Important distinctions between brief and sustained WWBs can also be made. Westerly anomalies typically extend above 200 hPa during brief WWBs but are generally confined to the lower troposphere (below 400 hPa) for sustained events. Sustained WWBs are also preceded by a quiescent period of reduced cloud thickness and surface winds that is accompanied by strong incident solar flux. Convective instability, as judged by a variety of techniques, increases by approximately 30% during this quiescent period. Brief WWBs do not include the precursory surface warming or convective destabilization of sustained WWBs. Notwithstanding the warming episodes before the events, sustained WWBs are associated with a net surface cooling approximately 40% larger than brief WWBs.The relationship between brief and sustained WWBs and the phase of the Madden‐Julian Oscillation (MJO) (as judged from outgoing long‐wave radiation) is also examined. Results support the classification of events as ‘brief’ and ‘sustained’ as used in this study, with brief WWBs occurring frequently during both wet and dry phases of the MJO, while sustained WWBs occur uniquely during the MJO wet phase. The association of brief and sustained WWBs with the MJO is shown to be independent of the El Niiio Southern Oscillation phase. It is therefore proposed that some, but not all, WWBs may be viewed as the surface signature of the MJO and that the mechanisms responsible for the MJO play an integral role in the formation and sustenance of sustained WWBs.

Analysis of Meteorological Precursors to Ordinary and Explosive Cyclogenesis in the Western North Pacific

Abstract Thirty-five cases of cyclogenesis that occurred during the cold seasons from 1975 to 1995 in the western North Pacific Ocean are studied to determine common and disparate dynamic and thermodynamic structures in both the ordinary and rapid developments. An analysis of 1000-hPa height and 1000–500-hPa thickness anomalies with respect to the 20-yr climatology reveals the following results. Though each sample of cyclogenesis is characterized by a favorable-appearing thickness trough–ridge structure, important differences are found. Both the upstream surface anticyclone and the downstream precedent cyclone are preferentially stronger at the beginning of the most rapid cyclogenesis in the strong sample. Because of the consequently stronger equatorward flow, the 1000–500-hPa thickness anomaly in the strong sample is colder by approximately 40 m (∼2°C) in the region of incipient cyclogenesis and eastward by 1500 km. A harmonic time series analysis of NCEP gridded fields partitions the geopotential height...

Simulation of the interannual variability of the wind-driven Arctic sea-ice cover during 1958–1998

A thermodynamic-dynamic sea-ice model based on a granular material rheology developed by Tremblay and Mysak is used to study the interannual variability of the Arctic sea-ice cover during the 41-year period 1958–98. Monthly wind stress forcing derived from the National Centers for Environmental Prediction (NCEP) Reanalysis data is used to produce the year-to-year variations in the sea-ice circulation and thickness. We focus on analyzing the variability of the sea-ice volume in the Arctic Basin and the subsequent changes in sea-ice export into the Greenland Sea via Fram Strait. The relative contributions of the Fram Strait sea-ice thickness and velocity anomalies to the sea-ice export anomalies are first investigated, and the former is shown to be particularly important during several large export events. The sea-ice export anomalies for these events are next linked to prior sea-ice volume anomalies in the Arctic Basin. The origin and evolution of the sea-ice volume anomalies are then related to the sea-ice circulation and atmospheric forcing patterns in the Arctic. Large sea-ice export anomalies are generally preceded by large volume anomalies formed along the East Siberian coast due to anomalous winds which occur when the Arctic High is centered closer than usual to this coastal area. When the center of this High relocates over the Beaufort Sea and the Icelandic Low extends far into the Arctic Basin, the ice volume anomalies are transported to the Fram Strait region via the Transpolar Drift Stream. Finally, the link between the sea-ice export and the North Atlantic Oscillation (NAO) index is briefly discussed. The overall results from this study show that the Arctic Basin and its ice volume anomalies must be considered in order to fully understand the export through Fram Strait.

Unusual electrical resistivity anomalies of thulium thin films at low temperatures

High precision electrical resistance measurements were performed in the temperature range from 4.2 K up to room temperature on a pure thulium bulk sample with a high residual resistivity ratio, RRR=146, and on thulium thin films in the thickness interval from 25 to 115 nm. The observed size-effect of the electrical resistivity is in accordance with theory and it is without resistivity vs. thickness anomalies. The typical “hump-backed” anomaly in the resistivity vs. temperature dependence was observed for the Tm bulk sample near the Néel temperature. In contrast, unexpected resistivity vs. temperature anomalies were observed for thulium thin films in the low temperature region below ∼60 K and near ∼170 K. A crystal structure study using X-ray diffraction revealed that these thin films were single phase with the Tm hcp crystal structure and with preferential orientation of crystallites.

夏季アジアモンスーンとENSOのカップリングのメカニズム

A significant coupling of the Asian summer monsoon and ENSO was examined using the NCEP/NCAR reanalysis for the period 1973-1995. Results show that a monsoon index, which is defined as meridional gradient of summertime upper-tropospheric thickness (200-500hPa) anomalies across 20°N over the Indian subcontinent, is highly correlated with Niño-3 SST anomalies in the preceding spring. This is strongly suggestive of the presence of the indirect impact of anomalous SST forcing associated with ENSO on the Asian summer monsoon.Due to attenuated Walker circulation in response to a warm episode, convection is suppressed over the northern tropical Indian Ocean and the maritime continent from the preceding winter to spring. The suppressed tropical convection in the preceding spring generates anomalous cyclonic circulation to the west of the Tibetan Plateau as a result of the Rossby-type response to convective heating off the equator. The convection-induced anomalous cyclonic circulation accompanied by large-scale ascending atmospheric motion contributes substantially to increased rainfall and greater soil moisture, thus resulting in decreased land-surface temperature over central Asia to the northwest of the Indian subcontinent. On the other hand, warm SST anomalies are initially introduced over the tropical Indian Ocean in late spring prior to the onset of the monsoon due to the changes in the surface heat flux and/or dynamic response of the ocean to wind forcing, in intimately association with pronounced in situ low-level northeasterly wind anomalies and less cloud cover. Both these different physical processes in the land and ocean areas are crucially responsible for reduced land-ocean thermal contrast (or reduced meridional tropospheric temperature gradient), eventually bringing about the weakening of the Asian summer monsoon. The reverse situation is quite true for strong monsoon years. Once the summer monsoon becomes weak (strong) at its early stage due to these processes, the initially induced warm (cool) SST anomalies over the tropical Indian Ocean are further intensified.The mechanism proposed here is valid during the period from the late 1970s to the early 1990s when weak and strong monsoon years are categorized. During that period, the unusual Niño-3 SST anomalies tend to persist from the preceding winter until summer, hence serving as a bridge between the ENSO prevailing in the preceding winter and anomalous summer monsoon. However, regardless of when the monsoon-ENSO coupling is prominent, both the springtime outgoing longwave radiation and low-level wind anomalies dominating over the tropical Indian Ocean, associated with anomalous Walker circulation, are still crucial factors in terms of the potential predictability of the Asian summer monsoon.

The Usefulness of MSU3 Analyses as a Forecasting Aid: A Statistical Study

A statistical analysis is performed on a 6-month global dataset consisting of satellite-derived channel 3 Microwave Sounding Unit (MSU3) brightness temperature and various conventionally derived fields to quantify the potential usefulness of MSU3 analyses in the nowcasting and forecasting of baroclinic waves. High positive spatial and temporal correlations are obtained between the MSU3 brightness temperature and 400‐100-mb thickness fields over all wavelengths in the data. Slightly lesser positive correlations are found between the MSU3 and the 200-mb temperature. The MSU3‐500-mb and MSU3‐50-mb height correlation results indicate a scale dependence in the hydrostatic spreading of thickness anomalies in the vertical. Most significantly, relatively high negative MSU3‐500-mb height correlations for the short (# synoptic scale) wavelength portion of the data suggest that upper-level thermal anomalies are reflected downward and that MSU3 analyses can be used to track midlevel synoptic-scale baroclinic waves. This conclusion is also supported by relatively high negative MSU3‐500-mb vorticity and MSU3‐dynamic tropopause correlations along the climatological storm tracks.