Observations

Steven J. Fletcher , in Information Assimilation for the Geosciences, 2017

14.1.ane Radiosondes

Radiosondes are battery-powered telemetry instrument packages that are carried into the atmosphere typically by a weather condition balloon; they measure distance, pressure level, temperature, relative humidity, air current (both speed and management), and cosmic ray readings at high altitudes. A grade of radiosonde whose position is tracked equally it ascends in the atmosphere to give current of air speed and direction is referred to as rawindsonde, which is an abbreviation for radar wind sonde. Another class of radiosondes are the ones that are released from airplanes and fall rather than being carried past weather balloons. This class of radiosondes are referred to every bit dropsondes. Radiosondes play a vital part in about forms of operational atmospheric data assimilation.

An important feature to note about the different forms of radiosondes is that the ascertainment may not occur at a model, or an assay, grid point, and as such there volition take to be some interpolation from the model to the location of the radiosonde observation equally nosotros only mentioned.

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OBSERVATIONS PLATFORMS | Radiosondes

W.F. Dabberdt , H. Turtiainen , in Encyclopedia of Atmospheric Sciences (2nd Edition), 2015

Components of the Mod Radiosonde

The radiosonde is an electronics unit that comprises three major sections: a suite of sophisticated meteorological sensors, signal-processing electronics, and a radio transmitter to relay the measurements back to a receiver at the radiosonde launch station. The meteorological measurements are fabricated at intervals that vary from 1 to half-dozen s, depending on the blazon and manufacturer of the radiosonde. The meteorological customs has been assigned two radio frequency bands for use in transmitting meteorological information: 400.15–406 MHz and 1668.four–1700 MHz. These bands are under continuing pressure from the telecommunications industry, which seeks to employ them for commercial, nonmeteorological purposes. All of the earth's radiosondes are required to meet certain performance standards that accept been established past the WMO (see Table 1). Figure iv illustrates four different radiosondes currently in use effectually the world.

Tabular array ane. Accuracy requirements (expressed equally standard error) for upper-air measurements for synoptic meteorology

Variable Range Accuracy requirement
Force per unit area Surface to five hPa ±1 hPa
Temperature Surface to 100 hPa ±0.5 Thousand
100–5 hPa ±ane K
Relative humidity Troposphere ±5% (RH)
Wind management Surface to 100 hPa ±5° for wind speed <xv m southward−1
±ii.v° for current of air speed >15 m s−ane
100–5 hPa ±5°
Wind speed Surface to 100 hPa ±1 m s−one
100–v hPa ±2 k s−1
Geopotential superlative of pregnant levels Surface to 100 hPa ±i% near the surface decreasing to ±0.5% at 100 hPa

World Meteorological Organization, 2008. Guide to Meteorological Instruments and Methods of Observation, seventh ed. Publication No. 8. WMO, Geneva.

Figure 4. Examples of radiosondes in current use effectually the world. Figures (a–c) from Wikipedia Commons; (d) from © Vaisala company, Helsinki, Finland. Reproduced with permission.

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Upper-Air Observations

Shawn Milrad , in Synoptic Assay and Forecasting, 2018

iv.1.one Radiosonde Instrumentation

The radiosonde i (rawinsonde) was invented in the late 1920s by Vilho Vaisala in Finland and independently by Pavel Molchanov in the Soviet Union. Radiosondes revolutionized our ability to measure basic atmospheric variables above the surface throughout the troposphere and stratosphere; previously, upper-air observations were expensive and quite sporadic. In modern times, these observations likewise serve as a crucial source of input data for numerical weather condition prediction (NWP) models. While the contents of the instrumentation bundle tin can vary slightly, standard radiosondes measure out vertical profiles of temperature, humidity, and pressure. Vertical profiles of air current speed and management are typically inferred from weather airship drift, using radiosonde trackers such as radio direction finders or Global Positioning Systems (GPS). Technically, the term rawinsonde 2 is reserved for atmospheric condition balloons with instrumentation that tin can make up one's mind current of air information, although in practice, radiosonde and rawinsonde are frequently used interchangeably.

The radiosonde instrumentation is contained within a small-scale white box attached to a weather condition airship that is filled with either hydrogen or helium (Fig. four.i). Fig. 4.ii shows a shut-upwards photo of typical radiosonde instrumentation. Similar to its ASOS counterpart (encounter Chapter 2), the temperature sensor uses the principle of electric resistance to measure temperature changes with altitude. The humidity sensor measures changes in ambient water vapor content by using substances that reply to such changes. Similarly to the ASOS force per unit area sensors (see Chapter 2), an aneroid barometer is used to measure out vertical changes in pressure level. Finally, the transmitter (Fig. iv.2) uses radio signals to relay existent-time radiosonde information back to a surface receiving system.

Fig. 4.1.

Fig. 4.1. Example of a radiosonde being launched with (lesser) small white box containing the standard instrumentation, (top) hydrogen or helium-filled weather condition airship and (eye) orange parachute.

 From the National Oceanic and Atmospheric Administration (NOAA) Globe Systems Research Laboratory (ESRL), available online at: https://world wide web.esrl.noaa.gov/gmd/obop/mlo/programs/esrl/ozonesondes/img/img_launching_sonde_hilo_1.JPG.

Fig. 4.2.

Fig. four.2. Close-up photo of the standard radiosonde instrumentation, as indicated. The aneroid barometer is located inside the white box.

 From the Hong Kong Observatory, available online at: http://www.hko.gov.hk/prtver/html/docs/wservice/tsheet/uamet.shtml.

The entire radiosonde instrumentation parcel is powered by a small battery located inside the white box (Fig. 4.two). Although it varies, a typical balloon tin rising up to 30   km above the surface, which is approximately the 10   hPa pressure level in the stratosphere. An boilerplate balloon rises at a rate of 300   m per min and, depending on winds, tin can drift as much as 200   km from the initial release point. Radiosonde instruments are generally considered accurate inside 1°C of temperature, 2   hPa of pressure, and v% relative humidity. Note that the instrumentation package is attached to a small parachute (Fig. four.ane); when the weather balloon finally bursts at high altitudes, the instrumentation bundle slowly floats dorsum to the surface. However, only about 20% of radiosondes are recovered, meaning that a global network is a relatively expensive endeavor.

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Chemistry OF THE ATMOSPHERE | Observations for Chemistry (In Situ)

H.Thousand.J. Smit , in Encyclopedia of Atmospheric Sciences (Second Edition), 2015

Radiosonde Force per unit area and Temperature

Errors in radiosonde pressure or temperature measurements will imply corresponding errors in calculated geopotential heights, causing measured ozone concentrations to be assigned to incorrect altitudes and pressures. This is potentially an important event for the derivation of trends, as radiosonde changes may therefore introduce vertical shifts in the ozone profile, and apparent changes in ozone concentration at a given height. A number of different radiosonde designs, from several manufacturers, have been used in the global observing network over the final 4 decades. At pressures beneath l hPa, meaning bias effects of v–10% in the ozone profile can occur, particularly for the radiosonde types used before 2000. Through the utilize of the Global Positioning Organization, modern radiosondes can measure geopotential heights with a higher accuracy. This will reduce any bias furnishings in the measured pressure, i.e., ozone profile significantly.

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Space Remote Sensing of Subtropical Oceans

Jay Chung-Chen , ... Mark Tepper , in COSPAR Colloquia Series, 1997

RESULTS

42 radiosonde and TOVS atmospheric soundings between Jan 16 - May vii, 1995 were compared graphically as shown in figures 3-6. The temperature profile (figure three) shows adept correlation between instruments, consequent with like comparing studies by. The dew point comparison was more scattered, however the profile remained similar as illustrated in figure 7. The current of air speed plots (figures 5 & 9) revealed a surprising systematic bias of 1.half dozen. This is explained by the breakdown of the geostrophic assumption away from the polar regions where the Coriolis force is not matched properly by the force per unit area gradient. Yet, the consistency of the data suggests a hidden relationship with latitude. Effigy 6 illustrates a "shot gun" pattern for air current direction measurements. Error analysis of the wind management in effigy ten exhibited a clear relationship between measurement fault and station breadth consequent with the above mentioned geostrophic breakdown. For example, Xisha at 16.89°Due north and Chenzhou at 25.nine°N recorded the highest and lowest errors respectively.

Figure three.

Figure 4.

Figure 5.

Figure 6.

Figure seven. Atmospheric Profiles Nigh Wuzhou Gathered By radiosonde and NOAA-12 TOVS soundings

Figure 8. Atmospheric Profiles About Hong Kong Gathered By radiosonde and NOSS-12 TOVS sounding

Figure ix.

Figure 10.

In addition, pronounced deviation at the lowest level (850 mb) illustrates terrain furnishings on wind speeds which is further illustrated past figure x. The comparisons shown in figures 7 & 8 for Wuzhou, PRC and Hong Kong present temperature, dew betoken, and wind speed & direction in situ measurements. In both graphs, the biased air current speed was corrected past a gene of 1.half-dozen as determined past figures 5 & 9. The TOVS wind direction measurement at 850 mb did not correlated with the radiosonde also suggesting terrain influences.

On June 6, 1995 Tropical Storm Deanna (figure 2) was located in a remote department of the S China Sea, which has an surface area of 2,319,000   km2. The TOVS wind field provided continuous details of the draft structure and movement. Local and regional forecast offices, including Hong Kong could estimate wind vectors at merely two levels past deject motions detected by sequential Geostationary Meteorological Satellite (GMS) images complemented by model output from large scale weather models. Combining radiosonde data from just 11 upper air stations weighted with kickoff gauge values from previous model output provided observational inputs. Conclusions

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On Fire at X

David A. Randall , ... David O'C. Starr , in Advances in Geophysics, 1996

6.9 Absorption of Upper-Air Data from Islands and Ships

Eight radiosondes per day were launched from Santa Maria, Porto Santo, the R/V Valdivia from Germany during the first iii weeks of the experiment and NOAA's R/V Malcolm Baldrige during the last week. Standard and meaning level data for virtually of these soundings were transmitted to Santa Maria, where they were transmitted to the Global Telecommunication System (GTS) by technicians from Lisbon's INMG (the Portuguese NWS). These data were and then assimilated into ECMWF and other global analyses. Approximately 650 of the 820 soundings were placed on the GTS, and about ninety% of these were assimilated into the ECMWF analysis. This was clearly a difficult merely major achievement. Assessments are in progress to make up one's mind how well the ECMWF analyses represent the boundary-layer structure and other fields during ASTEX. The ECMWF analyses will be used to ascertain large-scale divergence and other parameters needed to test regional and large-scale models.

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The jet stream and climate modify

Martin Stendel , ... Tim Woollings , in Climatic change (Third Edition), 2021

1.2 Jet streams and Rossby waves

The radiosonde networks spearheaded by Rossby in the 1930s–40s were crucial for identifying non but the hemispheric jet stream but likewise the planetary-calibration waves that at present behave his proper name (Fig. 15.1). Rossby waves are pervasive features of any large-calibration weather map and, in some sense, are more primal features of the atmosphere than fifty-fifty the jets themselves. These waves manifest as trains of alternating weather condition patterns—low pressure, high pressure, low force per unit area, and then on—generally arranged in a line roughly from west to east. These pressure anomalies are known, respectively, as cyclones (low pressure) and anticyclones (loftier pressure). If a jet stream is present, then the waves tin can be seen as meanders in the jet, as it snakes to the north and south of the weather systems.

Figure fifteen.1. A view of the subpolar jet stream (colored wavy streamlines depicting the wind speed, with dark cerise colors depicting the fastest winds) with an example of a Rossby wave in the Northern Hemisphere. Rossby waves atomic number 82 to positive ("+") and negative ("−") vorticity anomalies that class cyclones and anticyclones, respectively. For further give-and-take, see text.

 Figure adapted from an epitome past the NASA Scientific Visualization Studio.

Rossby waves arise from the conservation of vorticity, or informally "spin," in geophysical fluid dynamics. Vorticity comprises two components, 1 due to the rotation of air masses relative to the Globe'south surface and i due to the planetary rotation of the Earth itself. If an air mass moves poleward, for example, its planetary vorticity will increment because its local vertical axis is aligned more closely with the axis of the Earth. Its relative vorticity therefore has to subtract to recoup, and so it spins relative to the ground in the opposite management to the Earth, forming an anticyclone. The essence of Rossby waves is that neighboring air masses affect each other and can grow and propagate every bit waves of vorticity anomalies (e.grand., Ref. [half dozen]).

Rossby waves are idea to play a central function in the formation of jet streams in general. On large, planetary scales (on the gild of 5000   km), the atmosphere behaves in many ways like a two-dimensional fluid, with stirring introduced past the growth of vortices (eddies) in the unstable midlatitude regions. This growth, termed baroclinic instability , arises because of the strong meridional (n/south) temperature slope in the mid-latitudes. The instability arises considering common cold, dense air sits alongside warm, lighter air. In such a setting, ii-dimensional turbulence theory predicts that eddies should merge and grow to ever larger length scales. Nonetheless, the planetary rotation critically constrains the flow: Every bit the eddies grow, the efficiency of Rossby wave propagation increases until the wavelike parts of the flow dominate, and the disturbances propagate abroad as Rossby waves. The waves tend to ultimately propagate out of the midlatitude band, toward both the northward and south, and the structure of the waves in this state of affairs acts to send westerly momentum back into the cardinal region of the jet where the eddies grew. Hence, the "eddy-driven" jets are formed, without the need for an adjacent Hadley cell. These jets are common features of our oceans and the atmospheres of other planets every bit well as our own [vii,8].

In the absence of background winds, Rossby waves would propagate toward the west; however, the westerly winds typical of the midlatitudes blow, or "advect," the anticyclonic (clockwise) and cyclonic (counterclockwise) vorticity anomalies of the Rossby wave toward the east. When these two processes residual, i.e., the west Rossby wave propagation is equal to the due east advection by the westerly winds, a transient (propagating) wave becomes stationary . This is described physically as the wave having nothing phase speed, where the phase speed describes how fast the individual peaks and troughs of a wave propagate relative to the Globe. Such Rossby waves typically exist on conditions timescales (days to weeks), and thus, nosotros apply the term quasi-stationary to distinguish these waves from the stationary waves that are nowadays when taking a time boilerplate over many years for a item flavor. These stationary waves are largely forced by state–sea contrasts and mountain ranges (meet, due east.g. Ref. [iv]) and typically accept a larger spatial calibration than quasi-stationary or transient waves. Quasi-stationary waves are of particular importance for persistent weather and weather extremes, as we will meet in the side by side section.

The speed of Rossby wave propagation depends on the spatial scale of the wave, such that larger Rossby waves travel toward the eastward more than slowly than smaller Rossby waves. This means that the strength of the zonal wind required to make a wave stationary too depends on the spatial calibration of the wave [9]. As the zonal wind speed varies with time, breadth, and longitude, the spatial scale of the quasi-stationary waves will also vary. Thus, if there are changes in the boilerplate strength, breadth, or variability of the jets with a warming climate, the boilerplate spatial scale of quasi-stationary and stationary waves volition be affected (see Section ii.2).

An exact definition of quasi-stationary waves has yet to be agreed upon in the literature, but relevant studies typically expect at waves present in data averaged over 2   weeks to ane   month (e.g., Refs. [10,11,12]) or use quasi-stationary to refer to relatively short waves with nigh-zero phase speed [10]. Linear Rossby wave theory, together with observations of some events, suggests that at least some long-lasting quasi-stationary wave events are not simply one singular wave simply rather are recurrent Rossby wave events, in which a serial of transient, propagating waves all have phases that line upward, such as in Fig. fifteen.two [eleven].

Figure fifteen.ii. Hovmoller plots showing 250-hPa meridional wind averaged between 35° and 65°North during two carve up recurrent Rossby moving ridge events. Black dashed lines highlight the individual wave packets. Note that each wave package is propagating in space; however, the phase alignment of successive packages results in a quasi-stationary signal. Here, hPa refers to hectopascals or hPa.

In addition to shifting, pulsing, and stationary waves, a distinct form of jet variability is associated with a process termed atmospheric blocking (eastward.one thousand., Ref. [13]). This typically involves the local and temporary deflection of the jet and associated storm rails by a big-scale, persistent weather pattern, often involving a stationary anticyclone. Blocks typically last for a week or two, and this persistence can pb to severe weather impacts that often enhance seasonal contrasts, discussed further in Section 1.4.

The interaction between jets, Rossby waves, and blocking is complex and remains a topic of agile enquiry. While the jets, particularly outside of the subtropics, generally owe their being to the propagation of Rossby waves, the waves themselves are often strongly affected by the jets. Analysis of jet stream characteristics by Woollings et al. [14] supports the association of weaker jet stream winds with increased occurrences of blocks (eddies in the flow) and a larger variance in jet stream latitude, which can be interpreted as increased waviness (Fig. 15.three). Similarly, Blackport and Screen [fifteen] bear witness that weaker equator to pole surface temperature gradients, associated with weaker jets, leads to a "wavier" circulation (equally measured by local wave activeness), and vice versa, on interannual to decadal timescales. Interestingly, they did not observe this relationship to hold for longer-term changes, i.eastward., with anthropogenic climate change; this will be discussed further in Section ii.2.

Effigy 15.3. Time series of North Atlantic winter blocking and jet diagnostics from the 20CR reanalysis. All series take been smoothed with an 11-twelvemonth running mean.

 From [fourteen].

A jet stream manifests equally a concentrated gradient of vorticity, so that the jet locally enhances the background poleward gradient of vorticity owing to the rotation of the Earth. This gradient in vorticity is exactly where Rossby waves abound and propagate, and idealized moving ridge theories suggest that Rossby waves should bend toward strong and narrow jet streams. Indeed, in certain circumstances, jets tin act as atmospheric waveguides that locally trap the waves in a narrow band of latitudes [16,17].

Every bit noted before, the distribution of land and mountains on World creates zonal asymmetries in jet strength, which in turn creates zonal asymmetries in the atmospheric waveguides [16]. This is illustrated in Fig. 15.4, depicting the climatological mean zonal wind in the upper troposphere (the troposphere is the layer of temper from the surface to an altitude of approximately 14   km) in boreal summer (June–Baronial) in black contours (highlighting the jets), and the frequency of the presence of a local waveguide in colored shading. Zonal variations in the waveguides create variations in waves backdrop at different longitudes, with more zonal propagation in regions with stronger waveguides [18,19].

Effigy 15.4. Black contours showing the Northern Hemisphere midlatitude upper troposphere (300   mb) jet (zonal current of air; black lines, contour interval x   m/s) in boreal summertime. Shading shows the frequency of waveguide occurrence for wavenumber k   =   6. Come across Ref. [20] for details on the waveguide detection.

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Changes in the Atmospheric Apportionment as Indicator of Climate change

Thomas Reichler , in Climate Change, 2009

five.i Tropical Tropopause Heights

Analysis of radiosonde [36] and reanalysis information [37,38] shows that the height of the global tropopause has increased over the by decades, and GCM experiments indicate that anthropogenic climatic change is likely responsible for this increase [39]. This increment has been suggested equally a possible reason for the poleward expansion of the tropical circulation. For example, nearly inviscid theory for axisymmetric circulations, proposed by Held and Hou [40], suggests that the meridional extent of the Hadley circulation varies proportionally with the foursquare root of its vertical depth. However, applying this scaling to the past observed tropopause peak increase of about 200 m [39] leads to a tropical expansion of just 0.1° latitude per decade, which is less than what is suggested by the observations and by most models. Analyses of idealized [41,42] and more complex climate models [22,43] also demonstrated that the Held and Hou theory does not provide a skillful explanation for the full parameter dependence of the meridional extent of the HC.

Other studies have suggested that changes in tropopause heights poleward of the jet are cardinal to the poleward shift of the jet and the tropical edges [21,44,45]. These modeling studies take in common that the height of the tropopause is controlled past externally imposed temperature changes above or beneath the tropopause. Notwithstanding, this non only affects the height of the tropopause but also the meridional temperature gradients, the zonal winds, and the vertical air current shear by fashion of the thermal wind human relationship. The additional apportionment changes arrive difficult to unequivocally assign the cause for the tropical widening to the lifting of the tropopause. In add-on, none of the above studies puts forward a convincing physical mechanism by which tropopause height changes impact the position of the jets and the tropical edges.

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Poleward Expansion of the Atmospheric Apportionment

Thomas Reichler , in Climatic change (2nd Edition), 2016

5.three Tropopause Heights

Assay of radiosonde [154] and reanalysis data [155,156] shows that the height of the global tropopause has increased over the past decades, and GCM experiments indicate that anthropogenic climatic change is probable responsible for this increment [106,157]. The increase is related to systematic temperature changes below and higher up the tropopause [158]. Temperatures have been warming in the troposphere and cooling in the stratosphere, both of which have been shown to exist related to anthropogenic activity [159–161]. The pattern of warming and cooling also affects the zonal wind structure in the region of the subtropical upper troposphere and lower stratosphere (UTLS). This is related to the top construction of the tropopause. In the tropics, the tropopause is loftier and global warming reaches upwardly to ∼16   km. In the extratropics, the tropopause is low and warming reaches only up to ∼12   km, followed by cooling in the stratosphere above. Thus, at intermediate heights of the UTLS region (∼12–16   km) the tropics warm and the extratropics cool, leading to an increase in meridional temperature gradients, and, by the thermal wind relationship, to an increment of zonal wind speeds above.

Diverse studies related the lifting of the tropopause to the poleward expansion of the circulation [41,76,162]. According to a theory from Held and Hou [163], the meridional extent of the HC varies proportionally with the square root of its vertical depth. Nonetheless, applying this scaling to the past observed tropical tropopause superlative increase of about 200   m [154,157] leads to a tropical expansion of only 0.1° latitude per decade, which is much less than what is suggested by the observations and by most models. Analysis of arcadian [164,165] and circuitous models [41,94] also demonstrates that the Held and Hou theory does not provide a full explanation for the parameter dependence of the meridional extent of the HC, indicating that additional mechanisms are at work.

Some model studies suggest that lifting of extratropical tropopause heights is connected to poleward shifts of the jet and the tropical edges [76,126,166]. All the same, some caution is required. Studies lift the tropopause by imposing external thermal forcings to their models. This not only affects the height of the tropopause but other aspects of the atmosphere as well, like the meridional temperature gradient, the zonal air current, and the vertical wind shear. The additional changes make information technology hard to unequivocally assign the cause for the tropical widening to the lifting of the tropopause. In addition, lifting of the extratropical tropopause in itself notwithstanding does non provide a satisfying dynamical estimation for the poleward expansion. A study by Wu et al. [167] finds piffling evidence for the rise in tropopause leading to poleward jet shifts, arguing that an increase in the spatial scale of Rossby waves is responsible for the tropopause ascent and poleward shifting jets.

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