Abstract:
Airborne meteorological radars and related networks and models. In one embodiment a network for creating a meteorological model includes a mobile sensing node and a modeling node. The sensing node includes a meteorological RADAR that senses the wind velocity. Data from the meteorological RADAR regarding the wind velocity is received by a processor of the modeling node which determines a model of the wind from the wind velocity. The modeling node combines data from a second sampling node with the data from the first sampling node to create a resultant wind velocity vector. Preferably, the modeling node and the sampling node(s) communicate over an airborne WAN. Another embodiment provides a method of measuring the wind velocity. The method includes steering an RADAR signal out of the plane of travel of the mobile platform. The wind velocity is measured using a return of the RADAR signal.

Description:
RELATED APPLICATIONS 
   This application is a continuation in part of U.S. patent application Ser. No. 11/235,371, entitled Airborne Weather Profiler Network, filed by Tillotson on Sep. 26, 2005, which is incorporated herein as if set forth in full. 

   FIELD 
   This disclosure relates generally to meteorological radars and, more particularly, to airborne meteorological radars adapted to measure wind related Doppler effects with a high degree of resolution. 
   BACKGROUND 
   Current meteorological models are limited in their capabilities by the quality and quantity of available weather data. In particular, the sensors that gather weather data are few and far between in remote areas such as deserts, the polar regions, and oceans. The Eastern Pacific Ocean is one such example and has only a few weather buoys scattered along thousands of miles of United States coast. Since weather moves in from the Pacific in the western United States, the lack of data regarding the weather over the Pacific hinders the ability of forecasters to predict the weather in these coastal areas. Furthermore, while conditions near the ground can be readily sensed, conditions aloft can only be sensed remotely or on limited occasions (e.g. during the ascent of a radiosonde). Moreover, weather conditions can change rapidly thereby rendering what data has been gathered stale and inaccurate. In particular, wind measurements are an important part of the data that is needed to model the weather. For these reasons, among others, a need exists to improve the quality and quantity of readily accessible weather data including wind velocity data. 
   SUMMARY 
   It is in view of the above problems that the present disclosure was developed. The disclosure provides apparatus and methods to remotely measure wind vectors at multiple altitudes. 
   In a first embodiment, the present disclosure provides airborne meteorological radar units that measure wind data at many locations. The data gathered by these novel radar units includes wind speed and direction at all altitudes above the location where the winds are measured. The units also provide this data in a timely and frequent fashion. Preferably, the units ride aboard commercial transport aircraft although any type of aircraft (or other vehicle) could carry the radar units. Some of the advantages of mounting the radar units on large transports are that these aircraft over fly much of the globe, at all times of day and night, and do so on a frequent basis. Thus, the present disclosure provides a system that greatly expands the quantity and quality of wind, data available for use in weather models for example. 
   More particularly, the airborne meteorological radar units (hereinafter “weather radars”) provided by the present disclosure may be enhanced in several ways. In a first aspect of the present disclosure, the declination range of the airborne weather radars may be extended, so that the units can scan above and below the flight path. Preferably, the declination range extends in a downward direction to an angle of at least 45 degrees. For embodiments that use phased array antennas, it is that the phase shifters, or the software that controls the phase shifters, are configured and adapted to accomplish the improved declination range. In another aspect of the present disclosure, the weather radars are improved to directly measure the wind velocity and direction with a high resolution that heretofore has not been available from airborne radars. In other words, the airborne weather radars provided by the present disclosure are configured and adapted to make Doppler measurements of the wind velocity with a resolution of about 3 meters per second and wind direction with a resolution of about a tenth of a radian or about 5 circular degrees (assuming a 30 meters per second vertical wind speed). In contrast, previously available airborne radars measure the concentration of precipitation, not the wind itself. Moreover, these previously available radars are only able to resolve six discrete levels of precipitation. 
   In yet another aspect, the airborne weather radars provided by the present disclosure may also be configured and adapted to have range gates that are adjusted to enable the detection of the weak radar returns from atmospheric dust or water vapor. In other words, the range gates are adjusted so that these weak returns from close to the aircraft are allowed to pass to the detector rather than being discarded because they arrive before the range gate opens. 
   In still another aspect of the present disclosure, the airborne weather radars provided by the present disclosure are configured and adapted to sweep below (or above) the flight path of the aircraft on which they reside. More particularly, the scan patterns provided by the present disclosure can include sweeps wherein the surface of the Earth is scanned particularly when the airborne weather radar (or rather, the aircraft on which it resides) is over water. The returns from the water can thus be analyzed to characterize pre-selected surface attributes such as wave amplitude, wavelength, and direction of travel. Furthermore, this information can be correlated with low-altitude wind velocities over the body of water. This advantage of the present disclosure allows these low-altitude winds to be measured remotely despite the possibility that the weak radar returns generated by the atmospheric aerosols can be overwhelmed by ground clutter. Additionally, these surface returns may also be used for other types of remote sensing that are unrelated to winds velocity measurement. The present disclosure also provides a computer that combines navigation data from the aircraft with measurements of wind velocity made with airborne weather radars. The computer can be on the aircraft that carries the weather radar or on the ground, depending in part on the relative cost of air-to-ground communication verse onboard computational power. 
   In another embodiment, the disclosure includes networks, systems, and methods to combine wind velocity data from multiple airborne weather radars. Each of the wind velocity measurements may be made at different locations or some of the measurements may be made at the same location. In the case in which the measurements are made at the same location, the multiple measurements can be mathematically combined (for example by the root sum squares method) to improve the accuracy of the wind velocity measurement. One source of improvement in the measurement arises from the direction from which each of the multiple measurements is made. This is significant in that each Doppler velocity measurement detects one component of the velocity along the direction of the radar return. Thus, with multiple measurements made from different directions multiple velocity components are measured. These components can then be down-linked to a facility and analyzed to determine the overall wind speed and direction (i.e. the velocity). The analysis includes combining navigation data from the aircraft involved and the measured wind velocities. Accordingly, the present disclosure is relatively insensitive to sensing, or viewing, geometry. In another embodiment, the weather radar is configured and adapted to also scan to either side of the aircraft&#39;s flight path. 
   In yet another embodiment, the present disclosure provides a computer network for building weather models from the meteorological property profiles. The network of the current embodiment includes remote profiling instruments (e.g., “vertical profilers”) mounted on commercial aircraft, unmanned aerial vehicles, or other mobile platforms which are networked together via a communications network or system. Each of the vehicles therefore represents a sensing node of the network. Since the sensing nodes are mobile, the present disclosure allows gathering profiles over a larger region than was heretofore possible. A modeling node with a processor communicates with the sensing nodes to receive the gathered profiles and use them as inputs to a three dimensional weather model. The processor can also use the model to forecast the weather in the region where the profiles were gathered or even over adjacent areas. 
   Further features and advantages of the present disclosure, as well as the structure and operation of various embodiments of the present disclosure, are described in detail below with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate exemplary embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure. In the drawings: 
       FIG. 1  illustrates a system for measuring the wind that is constructed in accordance with the principles of the present disclosure; 
       FIG. 4  illustrates a method in accordance with the principles of the present disclosure. 
   

   DETAILED DESCRIPTION 
   Referring to the accompanying drawings in which like reference numbers indicate like elements,  FIG. 1  illustrates a wind vector measuring system constructed in accordance with the principles of the present disclosure. 
   The exemplary system  10  shown in  FIG. 1  includes several aircraft  12 ,  14 , and  16  equipped with airborne meteorological radar units (hereinafter “weather radars”) that typically detect precipitation  18  (shown schematically as a cloud) in the projected flight path of the aircraft  12 ,  14 , and  16 . Of course, the several aircraft  12 ,  14 , and  16  could instead be one aircraft shown at different times as it travels along its flight path. The weather radars aboard the aircraft  12 ,  14 , and  16  have been modified to detect the wind velocity v wind  not only along the projected flight path(s) but also in areas  20  offset from the flight path. For example, the area  20  where the wind velocity v wind  will be measured is shown in  FIG. 1  as being offset from the projected flight path both vertically and laterally by the distances h plane -h wind  ( FIG. 2)and d   plane -d wind  ( FIG. 1 ) respectively. In the general case, the various distances h plane -h wind  and d plane -d wind  need not be the same whether several aircraft  12 , 14 , and  16  participate in the system  10  or one aircraft  12  makes the multiple measurements from different locations. Of course, the aircraft  12 ,  14 , and  16  are also separated from the area  20  by, respectively, distances d 1 , d 2 , and d 3  in a direction parallel to the flight path ( FIG. 1 ). Regarding the flight path, it can be straight as shown or it may define a curvilinear trace through the atmosphere. Furthermore, each of the aircraft  12 ,  14 , and  16  have an orientation which is shown as being steady and level thereby defining a plane that includes the flight path and that is oriented in the same direction as the aircrafts&#39;  12 ,  14 , or  16  orientation. Of course, since the aircraft  12 ,  14 , and  16  can maneuver and reorient themselves, the plane defined by the orientation of the aircraft  12 ,  14 , or  16  reorients with the aircraft  12 ,  14 , or  16 . Nonetheless, the airborne weather radars on the aircraft  12 ,  14 , and  16  can scan substantially out of the plane and can scan laterally (in parallel with the plane) away from the flight path by a substantial angle. Thus, the airborne weather radars provide significant freedom in choosing where the wind velocity measurements may be made relative to the aircraft  12 ,  14 , and  16 . 
   When it is desired to make a measurement of the wind velocity v wind  at the location  20 , the weather radar signal is scanned to an angle α 1  in the x-z plane and an angle β 1  in the x-y plane. A pulse of electromagnetic energy (i.e., a RADAR signal) is then transmitted toward the location  20 . Dust, aerosols, particulates, and precipitation entrained in the wind at location  20  reflect the RADAR signal thereby causing a Doppler shift in the reflected signal. The weather radar unit about the aircraft  12  receives the RADAR return and detects the Doppler shift caused by the velocity of the material entrained in the wind. Accordingly, a measure of the wind velocity v wind  can be derived from the Doppler shift. By noting the current location of the aircraft  12  (via for instance a GPS system), the distance to the location  20 , and the angles α 1  and β 1 , it is possible to establish where the wind velocity measurement was made. 
   Of course, the Doppler shift is proportional to the component of the wind velocity Vwind that is parallel to the path of the RADAR signal. Accordingly, the sensed wind velocity Vwind from any given aircraft  12  at any given time may not sense the entire value of the wind velocity. However, another aircraft  14  at a different location can be used to obtain another measurement of the wind velocity vwind at the same location  20 . In the alternative, the first aircraft  12  may fly to a different location and make a second remote wind velocity measurement from that second location. With two different views to the location  20  of the wind velocity measurement, two wind velocity components can therefore be sensed by the system  10 . These wind velocity components, along with the locations of the relevant aircraft  12 ,  14 , or  16  and the deflection angles α, β of the radar signals, can then be mathematically combined to yield a resultant wind velocity measurement at the location  20 . Thus, the present disclosure allows airborne Doppler radars to measure true wind velocities instead of merely measuring a particular component of the wind velocity vwind where the viewing angles (e.g., α 1 , β 1  and α 1 , β 2 ) determine the component of the wind velocity that will be measured. In contrast, previously available airborne weather radar units are constrained to operate within small scan angles by the design requirements associated with the aircraft  12 ,  14 , or  16 . For instance, in the previously available weather radar units, the maximum vertical scan angle a is limited to 20 to 25 degrees. In. accordance with the principles of the present disclosure the declination scan angle of the airborne weather radars is increased to at least 45 degrees both above and below the flight path (or orientation) of the aircraft  12 . One method of accomplishing this modification to existing airborne weather radars, which use phased array antennas, is to add more phase shift values in the phased array to increase the declination angle α of the airborne weather radars of the present disclosure. In addition, the range gate of the airborne weather radars provided herein can be shortened to avoid detecting returns from ground clutter when the radar signal is steered to large deflection angles α below the horizon (and therefore the radar signal nears, or intersects, the ground). Thus one of the advantages provided by the present disclosure is that previous airborne weather radars could sense precipitation in only a small viewing area (or cone) in front of the aircraft whereas the present disclosure greatly expands the viewing area seen by the airborne weather radars. Accordingly, increasing the deflection angle α vastly increasess the amount of wind velocity data that can be made available for weather modeling. In a similar manner, the lateral deflection angles may also be increased beyond the range of the previously available airborne weather radar approaches in a similar manner. Thus, the airborne weather radars provided by the present disclosure can paint a more complete picture of the winds surrounding the aircraft  12 ,  14 , or  16  than the previously available approaches. 
   Preferably, the existing systems of the aircraft  12 ,  14 , and  16  can be modified to obtain the improved wind data from the airborne weather radars of the present disclosure.  FIG. 3  schematically shows an exemplary wind velocity measurement subsystem that has been integrated with the aircraft  12  of  FIG. 1 . The subsystem  48  includes a radar antenna  50 , a duplex switch  52 , an oscillator  54 , a radar transmitter  56 , a radar receiver or detector  60 , a crew display  62 , a processor  64 , a communication link to an aircraft navigation subsystem  66 , and an aircraft communication subsystem  68 .  FIG. 3  also shows a modeling node  70  in communication with the aircraft  12  which can be considered a sensing node. These devices  52 ,  54 ,  56 ,  60 ,  62 ,  64 ,  66 ,  68 , and  70  are interconnected as shown and cooperate to measure the wind velocity at locations  20  (see  FIG. 1 ) which are remote from the aircraft  12 . 
   More particularly, the oscillator  54  and transmitter  56  generate a radar signal or pulse and steer the pulse to the location  20  with the phased array antenna  50  which lies at the angles α and β relative to the orientation of the aircraft  12 . The radar return from the wind at the location  20  returns through the duplex switch and is routed to the detector  60  where the distance to the location  20  is measured along with Doppler shift caused by the wind. From the Doppler shift, the detector  60  determines the component of the wind velocity that lies in the direction of the radar return. The receiver  60  then places the wind velocity measurement on the aircraft&#39;s video data bus along with data regarding precipitation that the weather radar subsystem detects. This weather data is received on the crew display  62  and the processor  64  for display and analysis respectively. The processor  64  examines the data on the video bus and extracts the wind velocity measurements along with the angles α, β, α, β, and the distance to the measurement location  20 . Thus, the processor  64  can combine this data to determine where the location  20  is relative to the aircraft  12 . Additionally, the processor  64  obtains data related to the location of the aircraft  12  from the aircraft&#39;s navigation subsystem  66 . Using the navigation information, the processor  64  then determines the absolute location of the measurement location  20  and communicates the wind velocity information and the location  20  of the measurement to the aircraft communication system  68 . In turn, the communication system  68  transmits the information to the modeling node  70 . Of course, the modeling node  70  is likely to be in communication with other sensing nodes such as the aircraft  14  and  16  to obtain other wind velocity measurements. The modeling node  70  uses the wind velocity and location  20  information and, if desired, combines the wind velocity measurements at a single location  20  into a resultant wind velocity measurement. Also, the modeling node  70  builds a model of the weather in the region near the location  20 . 
   Thus, the airborne weather radars of the present disclosure can be configured to transmit the wind velocity data onto the aircraft&#39;s video bus  61 . The processor  64  can process the data on the video bus  61  to extract the various wind vectors, wind vector components (or radial vectors), and associated locations  20 . Since previously available airborne radars put weather data on the video bus  61  (for display in the cockpit), the video bus  61  is a convenient place to obtain the wind data without requiring modifications to the aircraft  12 . From the processor  64 , the wind data is down-linked to the modeling node  70  or a processing center on the ground. Of course, an existing processor or other circuit already on the video bus  61  could be reprogrammed to perform these novel functions. In the opposite direction, commands from the modeling node  70  can be up-linked to the aircraft  12  to direct the wind velocity subsystem  48  to measure the wind at locations  20  desired by the modeling node  70 . The commands can be forwarded to the transmitter  56  by the communication system  68  so that the transmitter can adjust the scan angles and range gates as necessary to comply with the modeling node  70  commands. 
   Turning now to  FIG. 4 , a method in accordance with the principles of the present disclosure is illustrated. Generally, the method  100  includes using an airborne weather radar to measure the velocity of the wind while the aircraft, on which the radar is located, is in flight. See operation  102 . The signal from the weather radar is steered out of the plane of the aircraft&#39;s flight path as in operation  104 . More particularly, the radar signal is steered to an angle greater than or equal to 45 degrees at some point in the flight. If desired, the range gate of the weather radar can be adjusted to avoid detecting ground clutter when the signal is steered toward the ground as in operation  106 . In the alternative, the range gate can be adjusted so that the weather radar picks up and measures features of the surface. More particularly, as shown in operations  108 ,  110 , and  112  if the aircraft is over (or near) a large body of water, the waves on the surface can be characterized and correlated with the winds in the vicinity. Of course, the airborne weather radar can be steered laterally in operation  114  in addition to being scanned vertically in operation  104 . 
   As shown at reference  116 , the range gate can be adjusted so that the airborne weather radar picks up signals at a close range. By adjusting the range gate in this manner it allows the weather radar to detect the weak returns from the wind near the aircraft. Since the entrained material that generate these returns are near the aircraft, the relative strength of the returns is larger than the equivalent returns from material at larger, conventional ranges from the aircraft. Because of the signal strength of these near returns, the airborne weather radar is able to detect the wind velocity with corresponding accuracy and resolution. Preferably, the range gate is adjusted to detect returns from just outside of the near field of the aircraft where the ambient air is un-affected by the passage of the aircraft through the atmosphere. 
   In any case, the airborne weather radar measures a wind velocity as illustrated in operation  118 . Operation  120  illustrates that, if desired, the foregoing operations shown by  FIG. 3  can be repeated. Or another aircraft can make a measurement of the wind velocity as shown at reference  122 . The second measurement can be of the wind velocity at the same location as the measurement made by the first aircraft. See operation  122 . Either, or both, of the wind velocity measurements may be communicated to a modeling node over an airborne wide area network (see operation  124 ). If more than one measurement is made at a particular location, then the two sensed radial components of the wind velocity can be mathematically combined (assuming that the two viewing angles were somewhat different) to yield the resultant wind velocity vector as shown by operation  126 . Once the measurements are made, they may then be incorporated in a meteorological model in operation  128 . From the model, nowcasts and forecasts of the weather can then be distributed in operations  130  and  132  respectively. 
   In operation, a typical wind measurement can be made as follows. An airliner, unmanned aerial vehicle, military transport, or other mobile platform that is equipped with a weather radar flies due north (zero degrees heading) at 35,000 feet. At 20,000 feet above the location where wind velocity data is desired the wind is blowing southeast (135 degrees heading) at 50 knots. As the aircraft is approaching the desired location but still several miles away, the weather radar is scanned downward at, for instance, 15 degrees to measure the wind velocity via the return signal. The measured Doppler shift associated with the wind entrained material is proportional to the dot product of the wind vector (135 degrees heading and zero vertical) and the radar vector (due north and 15 degrees downward). The weather radar emits another radar pulse, but at 30 degrees below horizontal. The measured Doppler shift for this pulse is proportional to the dot product of the wind vector (still 135 degrees heading and zero vertical) and the new radar vector (due north and 30 degrees downward). Again, the weather radar scans with the measured Doppler shift based on a radar vector that is now 45 degrees downward. Given the changing Doppler shift at each look-down angle, plus information about where the aircraft was located during each scan, the computer calculates the most probable wind vector at 20,000 feet above the desired surface location. The flexibility of the airborne weather radar provided herein thus allows one aircraft to hold the radar on a particular location while measuring the wind velocity as the aircraft flies by the measurement location. 
   In view of the foregoing, it will be seen that the several advantages of the disclosure are achieved and attained. The quantity and quality of wind velocity data is greatly expanded by the improved airborne weather radars provided by the present disclosure. Also, using aircraft to gather wind velocity measurements remotely in accordance with the present disclosure also greatly expands the availability and quality of wind velocity measurements. In turn, numerous benefits flow from the improved meteorological models that can be built using the improved wind velocity data. More specific benefits are described in U.S. patent application Ser. No. 11/235,371, entitled Airborne Weather Profiler Network, filed by Tillotson on Sep. 26, 2005, which is incorporated herein as if set forth in full. 
   The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical application to thereby enable others skilled in the art to best utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. 
   As various modifications could be made in the constructions and methods wherein described and illustrated without departing from the scope of the disclosure, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments, but should be defined in accordance with the claims and their equivalents.