Meteorological Impacts and Benefits of AMDAR Data Lee

Meteorological Impacts and Benefits of AMDAR Data Lee Cronce Ralph Petersen Cooperative Institute for Meteorological Satellite Studies (CIMSS) Space Science and Engineering Center (SSEC) University of Wisconsin - Madison AMDAR Regional Science and Technology Workshop Mexico City, Mexico 9 November 2011

Atmospheric Data Realities • • • Vertical variation of temperature, moisture and within the atmosphere is what drives Atmospheric Science In situ profiles of these data (i. e. , radiosondes) remain the backbone of any NWP analysis system The details within these profiles are especially important for recognizing and predicting hazardous weather events

Atmospheric Data Realities • • Vertical variation of temperature, moisture and within the atmosphere is what drives Atmospheric Science In situ profiles of these data (i. e. , radiosondes) remain the backbone of any NWP analysis system The details within these profiles are especially important for recognizing and predicting hazardous weather events The locations of radiosonde sites are sparse, and the number of radiosonde reports is decreasing worldwide

Atmospheric Data Realities • • • Vertical variation of temperature, moisture and within the atmosphere is what drives Atmospheric Science In situ profiles of these data (i. e. , radiosondes) remain the backbone of any NWP analysis system The details within these profiles are especially important for recognizing and predicting hazardous weather events The locations of radiosonde sites are sparse, and the number of radiosonde reports is decreasing worldwide Satellites provide global coverage; however, not at detail necessary (especially near the surface) AMDAR fills this void!

AMDAR in a Nutshell • Temperature and Wind Observations from Commercial Aircraft – High quality, high resolution data – Available at: • Flight Level • In Ascent / Descent – Instruments already on aircraft – Economical (~100 times less expensive than radiosondes) – Asynoptic (not only available at 00 and 12 UTC, not a problem for NWP) – Looks, feels, tastes like radiosonde data – Retrieved through ACARS and MDCRS

Usage of AMDAR Data WHO WOULD BENEFIT FROM THIS DATA SOURCE?

How does NCEP use AMDAR data? In all of its atmospheric models • NCEP runs a suite of Atmospheric and Oceanic models to meet a variety of user needs. AMDAR data are used in: – Climate (Coupling Atmosphere and Ocean) – Global (Medium Range Forecasts) • 4/day - Deterministic and Probabilistic – Mesoscale (Higher-Resolution Weather Forecasts) • 4/day - Deterministic and Probabilistic • Rapid Update Cycle (RUC) [soon to be Rapid Refresh Model] – Hourly - Aviation and Hazardous Weather » Mexico included in coverage, so immediate use available

How does NCEP use AMDAR data? In all of its atmospheric models • Vertical profiles of wind, temperature and humidity are the foundation of every NWP system • NCEP has been using AMDAR data in its NWP models for over 10 years • Over 300, 000 reports arrive daily – Data delivered in real-time 24 hours daily – Most contain wind and temperature only • Increasing numbers include humidity – The data arrive in BUFR format • The program is a cooperative venture between data providers and users – Everyone benefits from the results

How does NCEP use AMDAR data? In all of its atmospheric models “Rule of Thumb” • In Numerical Weather Prediction (NWP), one bad observation does more damage than the benefit that comes from 100 good observations! • AMDAR data are extremely accurate and reliable, but – Good Quality Control of all observations is essential • Requires multiple observations

A major advantage of AMDAR data – multiple observations corroborate each other Weekly Data counts by Cycle

Data Volume/Coverage by Layers Six hours of data Note locations Of Ascent/descent Reports ←← 300 -100 mb 700 -300 mb 1000 -700 mb

FORECAST IMPACTS OF AMDAR DATA

Determining Forecast Improvement from increased AMDAR volume – Use Wind forecasts as a measure of impact General Observation • During weekday, when more AMDAR reports are available, short range forecasts are consistently better • 0000 -1200 UTC (overnight) AMDAR volume average • Tu-Sa >70, 000 reports • Su-Mo only ~25, 000 reports • Difference is primarily due to lack of parcel delivery flights

Quantifying these Observations using the Rapid Update Cycle - RUC is designed to produce hourly analyses and updates to very short range forecasts (0 -12 hrs) § Real-time 1 -hourly analysis/forecast cycle § Analyses intended to fit data very closely § Forecasts only from 3 to 12 hours into future § In general, 3 hr RUC wind forecasts are more accurate than 12 hr forecasts § Examination of verification against § Radiosonde observations

Weekend minus Weekday 3 hr Wind Forecast Errors for Jan-Oct RUC Wind forecasts -Verification against raob data Off-time data on weekends produces less impact, especially after reduced overnight package carriers reports 0. 35 m/s / ~5. 0 m/s = 7% better forecasts during weekdays due to more AMDAR reports at 200 h. Pa

2 -8 Sept 01 Hourly AMDAR Volume Received at FSL (ESRL) Su Mo Tu We Th Fr Sa 2 -15 Sept 01 (starting 00 z 2 Sept) 9 -16 Sept 01 Notable reductions of aircraft data available to RUC at FSL on weekends and immediately after Sept. 11, 2001 Su Mo Tu We Th Fr Sa

Improvement in 3 hr over 12 hr wind forecasts during September 2001 Forecasts from operational RUC run at NCEP 11 -13 September 2011 • No AMDAR data • 20% loss of 3 hr RUC wind forecast skill at 250 mb • 3 hr fcst skill ≅ 12 hr skill • No skill added by other off-time reports!!! Period of data outage 11 -13 Sept 2001 RUC 250 mb wind forecasts verified against raob data

Impact of AMDAR Ascent/Descent Data in Rapid Update Cycle (RUC) forecasts EMC OSE by Ralph Petersen, Geoff Manikin and Dennis Keyser • Test performed using operational 20 km RUC – Ran data assimilation / forecast system for 3 weeks in June 2002 using two configurations: 1. Including all data 2. Eliminated aircraft data below 350 h. Pa – – Kept High-level En-route Data Ignored Ascent /Descent Data – Compared analyses and all forecasts (3, 6, 9, 12 Hr) against radiosonde at 00 and 12 UTC over CONUS – Results expressed in improvement due to Ascent/Descent Data

Impact of AMDAR Ascent/Descent Data in Rapid Update Cycle (RUC) forecasts • Question 1 – What was the effect of the addition of ascent/descent data on the data assimilation system and resulting 00 and 12 UTC analyses?

Normalize error: compares forecast differences with overall forecast error • Significant improvement by including Ascent / Descent data • Positive effects at all levels • Greatest effect at 30, 000’ and below • Positive impact on Winds, Temp and RH.

Impact of AMDAR Ascent/Descent Data in Rapid Update Cycle (RUC) forecasts • Question 2 – What was the effect of these analysis differences on the 12 hr forecasts?

Tropospheric Improvements up to twice those in changing RUC from 40 to 20 km • Significant improvement by including Ascent / Descent data • Positive effects at all levels on Winds, Temp and RH • Above 25, 000’, impact comparable to analysis differences • Below 25, 000’, impact still large - but slightly smaller than in analysis

Impact of AMDAR Ascent/Descent data in Rapid Update Cycle (RUC) forecasts • The fundamental purpose of the RUC is to use ‘off-time’ data to make repeated corrections to traditional ‘on-time’ model guidance • Question 3 – How did the continued data assimilation affect model performance?

Tropospheric Improvements are 2 -3 times greater than those in changing RUC from 40 to 20 km • After 9 hrs of continued use of ascent/descent data, tropospheric forecasts have improved by yet another 1 -2%

Impact of AMDAR Ascent/Descent data in updating operational RUC forecasts Descent 10– 20% improvement at all levels from forecast updates 12 Hr Forecast Error – Red 3 Hr Forecast Error – Blue Both forecasts valid at same times

Impact of AMDAR Ascent/Descent Data in Rapid Update Cycle (RUC) forecasts • The fundamental purpose of the RUC is to use ‘off-time’ data to make repeated corrections to traditional ‘on-time’ model guidance • Overall question now becomes: – How much of the impact was the result of including ‘off-time’ ascent / descent data?

Difference between 12 hr operational RUC forecast and a later 3 hr forecast (valid at the same time but using additional asynoptic reports) from systems with & without ascent/descents Descent Lack of ascent/descent data in assim. /fcsts eliminates virtually all tropospheric benefits of off-time updates and degrades upper-levels Assimilation/forecasts with Ascent/Descent Data– Red Assimilation/forecasts without Ascent/Descent Data– Blue

LOCAL APPLICATIONS OF AMDAR DATA

Local Applications • Severe Weather – Capping Inversions – Convective Instability – Wind Shear • Precipitation and Type – Timing, Location, Intensity • Fog Onset/Dissipation – Trapping Inversion Development/Decay – Calm Winds • Air Quality/Fire Weather – Wind, Stability, Mixing, Extended Coverage

Low-Level Wind Shear • Green Bay, Wisconsin, 29 October 2005 • LLWS was forecast to begin after 0600 UTC in the TAF • Aircraft soundings near 0120 UTC already showed LLWS • Based on this observation, the aviation forecaster was able to update the TAF and begin the LLWS more than 3 hours earlier than the prior forecast.

Low Ceilings, Visibilities and Fog • Detroit, Michigan, 4 February 2005 • Soundings near 2230 UTC showed light boundary layer winds, near -surface moisture, dryness above • Commonly favorable conditions for fog development • Based on the observations, the TAFs for 09 and 12 UTC were amended, reducing visibilities to ½ mile. • METARS showed that visibilities did decrease KDTW 0532 z 00000 kt 2 sm br clr KDTW 0739 z 17003 kt 1 3/4 sm br r 04/ 1000 v 3500 KDTW 0936 z 17004 kt 1/4 sm fg r 04/ 0500 v 0600 KDTW 1154 z 16004 kt 1/4 sm fg r 04/ 2800 v 0600

Precipitation Type • Buffalo, New York, 15 December 2005 • Forecasters initially were calling for larger snow accumulations • AMDAR temperature profile shows a larger than expected warm layer aloft • With the existence of this deep warm layer aloft, forecasters amended the forecast calling for smaller snow accumulations and increased chances for sleet and freezing rain

Convective Storms • Central Wisconsin, 6 July 2005 • Linear mesoscale convective system expected to persist into Wisconsin • Severe thunderstorm watch was issued at 1530 UTC for most of Central Wisconsin

Convective Storms • Aircraft soundings from watch area at watch issuance and later showed strong capping inversion unlikely to break • Forecasters lowered the chance for storms and the severe thunderstorm watch was cancelled

Fire Weather • Northern and Central Wisconsin, 15 June 2006 • Aircraft data showed extremely dry conditions coupled with the potential for high winds due to mixing • Very dry air could be seen on aircraft soundings earlier in the day when the Red Flag Warning was issued • Later soundings showed there was sufficient dry air in other parts of the forecast area to expand the warning • Temperature >75 F, RH <25%, winds >25 mph

In Summary • AMDAR is a very important and necessary data set • Fills spatial and temporal voids apparent in radiosonde and satellite data sets • En-route data, but more so, ascent/descent data are vital to NWP skill • Not just a NWP benefit, but an important local forecast area data set