1 / 20

Selected CalWater AR Accomplishments

This study examines the kinematic and thermodynamic structures of Sierra Barrier Jets (SBJs) and Atmospheric Rivers (ARs) during a land-falling winter storm in Northern California. It analyzes the observations from radar retrievals, wind profiler time series diagnostics, and balloon soundings. The study also compares long-term wind profiler observations with reanalysis datasets, highlighting the representation of SBJs. The impacts of ARs on soil moisture and runoff are also assessed. Additionally, the validation and implications of AR forecasts are discussed, highlighting the uncertainties in location and the need for improvements.

sylviar
Download Presentation

Selected CalWater AR Accomplishments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Selected CalWater AR Accomplishments

  2. AR-SBJ IOPs 3-7 in Feb/Mar 2011 AR-SBJ IOPs 1-2 in Dec 2010

  3. Summary – three field seasons from 2009-2011 • 13 Sierra Barrier Jet events observed during IOPs • 4 strong (> 25 m/s) • 7 moderate (15-25 m/s) • 2 weak (< 15 m/s) • 10 Atmospheric river events observed during IOPs • 1 strong • 7 moderate • 2 weak

  4. Kinematic and Thermodynamic Structures of Sierra Barrier Jets and Overrunning Atmospheric Rivers during a Land-falling Winter Storm in Northern California Kingsmill, Neiman, Moore, Hughes, Yuter and Ralph Journal of Hydrometeorology, 2013 • Landfalling storm 14-16 February 2011 • Multi-Doppler scanning-radar retrievals • Multi-wind-profiler time series diagnostics • Balloon soundings • Observing network clearly monitored both the AR and SBJ during two sub-periods within the 2-day IOP • SBJ western edge detected • SBJ deepened toward the north • AR rode up and over the SBJ

  5. Sierra Barrier Jets, Atmospheric Rivers, and Precipitation Characteristics in Northern California: A Composite Perspective Based on a Network of Wind Profilers Neiman, Hughes, Moore, Ralph, and Sukovich MWR 2013, in press (July 2013) *Schematic based on a composite of the 13 strongest SBJ cases observed at the SHS profiler between 2009-2011. *Profilers at CCO, CFC, and CCR also recorded data and composited during these SBJ cases. *A 6-km regional reanalysis dataset from the WRF model provided additional information. *The SBJ parallels the Sierra over the eastern Central Valley (CV): core 1 km above ground. *The SBJ core increases in altitude up Sierra windward slope and poleward over Nern CV. *Inland penetration of AR through San Francisco Bay gap contributes to SBJ deepening/moistening over Nern CV. *Aloft, AR airstream rides over SBJ. *Sierra-perpendicular vapor fluxes linked to heavy precip. along Sierra’s windward slope, & SBJ-parallel fluxes tied to heavy precip. at N end of CV.

  6. Representation of the Sierra Barrier Jet in 11 years of a high-resolution dynamical reanalysis downscaling compared with long-term wind profiler observations. Hughes, M., P. J. Neiman, E. Sukovich and F. M. Ralph, 2012, J. Geophys. Res. – Atmos.,117 NARR 32 km grid size RD 6 km grid size • Method • 11 years of profiler-observed SBJs (256) • Compared with reanalyses ranging from 275 km, 32 km, 10 km to 6 km grid sizes • Results • NNRP (275 km) does not have SBJs • NARR (32 km) and CARD (10 km) SBJ is 2 times as deep as observed • WRF RD (6 km) has 80% of SBJs • SBJs in WRF RD (6 km) are best match to observed strength and depth • WRF RD misses stable layer below 500 m MSL in SBJs (compared to radiosondes) • Vapor transport in 6-km WRF-RD differs greatly from 32-km NARR • NARR 35% too much flux into Sierra • NARR 20% too little flux along Sierra

  7. Atmospheric Rivers in IPCC-AR4 climate-change projections by 7 modern GCMs Obs case • By end of 21st Century, most GCMs yield: • More atmospheric vapor content, but weakening westerly winds • Net increase in “intensity” of extreme AR storms • Warmer ARs (+1.8 C)  snowline raised by about 1000 feet on average • Lengthening of AR seasons (maybe?) Water Vapor & Low-Level Winds Dettinger, M.D., 2011, Climate change, atmospheric rivers and floods in California—A multimodel analysis of storm frequency and magnitude changes: Journal of American Water Resources Association, 47, 514-523.

  8. Observed Impacts of Duration and Seasonality of Atmospheric-River Landfalls on Soil Moisture and Runoff 10 longest duration ARs (>31 h) Average of all 91 ARs F. M. Ralph1, T. Coleman2, P.J. Neiman1, R. Zamora1, and M. D. Dettinger3 (J.Hydrometeor., 2013)

  9. Validation of AR Forecasts – Results/Implications While overall occurrence well forecast out to 10 days, landfall is less well predicted and the location is subject to significant errors, especially at longer leads • Errors in location increase to over 800 km at 10-day lead • Errors in 3-5 day forecasts comparable with current hurricane track errors • Model resolution a key factor RMS Error in Forecast AR Landfall Location From Wick et al., 2013, Weather and Forecasting • Models provide useful heads-up for AR impact and IWV content, but location highly uncertain • Location uncertainty highlights limitations in ability to predict extreme precipitation and flooding • Improvements in predictions clearly desirable

  10. Planetary- and synoptic-scale conditions in aMarch 2005 case From Ralph et al. 2011, Mon. Wea. Rev.

  11. Madden Jullian Oscillation impacts Sierra Snow: Guanet al. (2012; Mon. Wea. Rev.) Guan et al. (2012; Mon. Wea. Rev.) Snowpack in the Sierra acts as a natural and Important reservoir for CA. Snowfall often comes in powerful winter storms, sometimes with Atmospheric Rivers. Snowpack in the Sierra acts as a natural and Important reservoir for CA. Snowfall often comes in powerful winter storms, sometimes with Atmospheric Rivers. • The MJO modulates snowfall rates. • Phase 3 -> + 30-50% • Phase 8 -> - 30-50% • Implied Predictability? • Source of moisture? • The MJO modulates snowfall • Rates. • Phase 3 -> + 30-50% • Phase 8 -> - 30-50% • Implied Predictability? • Source of moisture? The MJO is a large-scale phenomenon that could also influence Russian River precipitation 11

  12. Atmospheric Rivers, Floods and the Water Resources of California by Mike Dettinger, Marty Ralph, , Tapash Das, Paul Neiman, Dan Cayan Water, 2011 25-35% of annual precipitation in the Pacific Northwest fell in association with atmospheric river events An average AR transports the equivalent of 7.5 times the average discharge of the Mississippi River, or ~10 M acre feet/day 35-45% of annual precipitation in California fell in association with atmospheric river events

  13. What is the Palmer Drought Severity Index (PDSI) doing (on average) in the months before & after drought breaks? Dettinger, Michael D., 2013: Atmospheric Rivers as Drought Busters on the U.S. West Coast. J. Hydrometeor, 14, 1721–1732. 1895-2010

  14. Distributions of average PDSI steps across PDSI=-2 at 344 climate divisions Dettinger, Michael D., 2013: Atmospheric Rivers as Drought Busters on the U.S. West Coast. J. Hydrometeor, 14, 1721–1732. 40% of NorCal drought breaks involved ARs Percentage of Persistent Drought Breaks, 1950-2010

  15. Up to > 12 inches of rain – some drought relief CalWater-2* “Early Start” field campaign 3-25 February 2014 Summary Courtesy of Marty Ralph UCSD/Scripps/Center for Western Weather and Water Extremes This AR increased precipitation-to-date from 16% to 40% of normal in < 4 days in key Northern California watersheds, but runoff was muted due to dry soils. “Frontal wave” Flight area for NOAA’s G-IV aircraft on 8 Feb 2014 Goal: developing AR flight method to sample a “frontal wave” that can cause an AR to stall over one area at landfall (G-IV PI: Chris Fairall – NOAA; Mission Scientists: Marty Ralph – Scripps, Ryan Spackman – STC) Russian River’s highest flow in > 1 year *CalWater-2 is a 5-year program (from 2015-2019) proposed to focus on West Coast precipitation processes and how a changing climate will affect them. It is led by UCSD/Scripps with partners from DWR, CEC, NOAA, NASA, DOE and others. Hawaii SSM/I satellite observations of water vapor on 8 Feb 2014 (Courtesy G. Wick, NOAA)

  16. NOAA G-IV Flight Crew

  17. IOP 5 Integrated Vapor Transport (kg m-1 sec-1) Start: 13-Feb-2014 18:33Z End: 13-Feb-2014 20:58Z IVT > 250 kg m-1 s-1 • Total AR transport • IVT threshold: 6.9 x108 kg s-1 • IWV threshold: 4.3 x108 kg s-1

  18. IOP 5 23 Total Sondes Deployed Use 17 Sondes that were approx equally spaced AND where AR criteria met (IVT > 250 kg m-1 sec-1) => sondes 4 thru 20 (white box)

  19. control CASE 1 (N=17) CASE 2 (N=9) CASE 3 (N=5) CASE 4 (N=3) CASE 4A (N=3) CASE 4B (N=3) Vary sonde resolution and recalculate total IVT across AR section Maintain same physical width of AR section 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 72.5 5.89 4 6 8 10 12 14 16 18 20 145 5.85 (-1%) 4 8 12 16 20 290 5.54 (-6%) 4 12 20 580 4.89 (-17%) 4 11 20 580 6.43 (+9%) 4 13 20 580 4.64 (-21%) Avg Spacing (km) AR Transport (108 kg sec-1)

  20. Uncertainty in predicted extreme surface winds found to be associated with an AR Doyle, James D., Clark Amerault, Carolyn A. Reynolds, P. Alex Reinecke, 2014: Initial Condition Sensitivity and Predictability of a Severe Extratropical Cyclone Using a Moist Adjoint. Mon. Wea. Rev., 142, 320–342 “The sensitivity maxima are found in the low- and midlevels, oriented in a sloped region along the warm front, and maximized within the warm conveyor belt. The moisture sensitivity indicates that only a relatively small filament of moisture within an atmospheric river present at the initial time was critically important for the development of Xynthia.” Adjoint sensitivity valid at the initial time of 1200 UTC 26 Feb 2010 at 700 mb for water vapor (color coded). Hatched area is water vapor mixing ration >4 g kg-1.

More Related