lake superior north shore climate jim zandlo state climatology office dnr-waters 2006

Lake SuperiorNorth Shore Climate

Jim Zandlo

State Climatology Office

DNR-Waters 2006

Superior ClimateSuperior Climate

• 2005-06 snow season

• Dry summer, low lake


• 2005-06 snow season– More-or-less ‘normal’ precipitation

• spring runoff was (probably) more-or-less ‘normal’

– Snowfall pattern very similar to 4-year SnowRules! result

– climate.umn.edu/SnowRules then click on 2005-06 map

A slow start in NE (again) …

Snowfall Dec 13-19, 2005

… right past ‘normal’ snow depth

Snow fall N ov 2005 - Apr 2006

W olf R idge

Tw o H arbors

G rand M ara is

Snowfall Four season average 2002-06

W olf R idge

Tw o H arbors

G rand M arais

Snowfall Nov 2005 – Apr 2006


• 2005-06 snow season– Snowfall transect updated

• Fraction of median (was fraction of max)

• Log-of-distance spreads out values close to Lake Superior

– climate.umn.edu/SnowRules then click on 2005-06 map

Superior Climate


• Dry summer– Low Lake Superior– Basic hydrology

• GLERL time series

Superior Climate


• Dry summer– Near record low water levels (1925-26)

on Lake Superior– Basic hydrology

• Summer is primary recharge period for Lake Superior


• What happens next?

A range of almost 4 feet in the observational record.

Lake Level:

Lake level = old lake level + precipitation on lake

+ runoff from surrounding land (flow in)

- lake evaporation

- flow out at outlet (Sault Saint Marie, MI)

+/- groundwater flow

Basic Lake Hydrology

Geography and General Hydrology

- large, ‘state-sized’ watershed- ‘narrow’ along American shore

Water for runoff, cisterns

Water coming in …

Runoff 37%

Precipitation 59%on lake

Diversion 4%

…must go out (most of the time)

St. Mary’s River 57%

Evaporation 43%Deposition

0.2%

Water coming in …

Runoff 1.7 ft

Precipitation 2.7 ft

Diversion 0.2 ft

…varies

Deposition 0.2%

Year ending 11/1985 had 10% more

water

Year ending Feb 2001 had 15% less

water



Runoff 1.8 ft

Runoff 1.1 ft

Future developments?(What happens next?)


Lake Superior evaporation …

Lake Superior evaporation …

is not the same as evapotranspiration from nearby land surfaces

NOAA Buoys-meteorological parameters-sea measurement

-wave info-water temperature

-

Lake Evaporation equationLake Evaporation equation

• Evaporation = factor * D‘factor’ varies with weather, surface

conditions, etc.‘D’ is the difference in vapor pressure

between two different air masses

• If this year’s atmospheric humidity was essentially ‘normal’ (don’t know yet) then using the above equation, evap would have been about 0.5 foot more than ‘normal’ this Aug-Oct.

Lake Evaporation equationLake Evaporation equation• September water at

9+°F ’above normal’ has cooled to a little more than 5+°F by Oct 23. The water will tend toward 32°F (and be ‘more normal’) as winter progresses.

• If water temperature becomes ‘normal’ by mid-winter, an additional

0.2 feet or more than ‘normal’ can be expected to evaporate from the lake this winter.


Lake Level:

Where will it actually end up?

Winter 2006-07 Outlook (a strong ‘el nino’ influence)

Let it snow! Varley

Lake SuperiorNorth Shore Climate

Jim Zandlo

State Climatology Office

DNR-Waters 2006

(thermochrons)

Thermochrons, transectsThermochrons, transects

Thermochrons, the dime sized devices that measure and store thousands of temperatures, are being used throughout the SnowRules! study area to gather temperatures where the snow falls, namely on snowboards. They are also being used to get air and water temperatures at a few other locations. See the data at climate.umn.edu/SnowRules

f

° F at 5/28/2006 12:00

Let it snow!

Superior Climate


• Dry summer– Near record low water levels (1925-26)

on Lake Superior– Basic hydrology

• Summer is primary recharge period for Lake Superior


• What happens next?

Let it snow!


Lake Level:

Superior Climate Superior Climate

• Geography and Hydrology

• Summarizing the observations– Normal Temperature– Satellite-based measurements– Is it ‘elevation’ or ‘the lake’– Normal Precipitation– Snowfall patterns– Temperature versus snow

Great Lakes Hydrology (climate)Great Lakes Hydrology (climate)

• Basin maps: limited detail

• Balance of incoming/outgoing– Superior evaporation smaller fraction of

precipitation than other great lakes

• Lake levels are ‘integrator’

Cold!

CoolDry

Evapo-transpirationEvapo-Evapo-transpi-transpi-rationration

RunoffRunoff


Lake Level:

HydrologyHydrology is ‘forced’ by climateis ‘forced’ by climate

• How do patterns arise?– ‘weather patterns’– cool/warm water nearby– topography

• (Water flows downhill)

• topo temp evap runoff

– All the above interacting (!)

• What do patterns of ‘climate’ variables look like?

Wind – winter transectWind – winter transect

• Inland: mostly N-NW or S-SW • Shore: strong tendency to ‘follow’• Can transport air masses across the

shoreline

Hibbing Grand Marais airport Grand Marais shore

Wind – winter along shoreWind – winter along shore

• ‘Everywhere’ along shore has strong tendency for ‘along shore’ winds in winter

Two Harbors Silver Bay Grand Marais shore

Wind – seasons at Grand MaraisWind – seasons at Grand Marais

Tendency to be ‘along shore’ less in summer

Air moisture (air mass)Air moisture (air mass)

Normal TemperatureNormal Temperature

• Biggest near shore influences near equinoxes– Land near seasonal extremes– Lake ‘lags’ land by a month or two

• Detail limited by 25-mile NWS observer spacing

winter(DJF) spring(MAM) summer(JJA) fall(SON)

Satellite-based ice observationsSatellite-based ice observations

• Most of Minnesota averages less than 2 months.

• Much of north shore not until Feb

• ‘ice out’ by early to mid-March

20 years of buoy data at red circle. No mid-winter buoy data is available.

Commonly open water in mid-winter means a large wet surface near 32 degrees is often near the north shore anytime during winter.

Land versus ‘sea’Land versus ‘sea’

Two Harbors and Grand Marais temps ‘buoyed up’ in winter, ‘anchored’ to lower values in summer.

Water maximum lags land maximum.

Land versus ‘sea’

Shore virtually identical in winter to MSP 150 miles south!

At Babbitt about 6 F cooler than MSP year-round.

Land versus ‘sea’Land versus ‘sea’

Temperature is also affected by elevation. Some of the steepest gradients of the Great Lakes are along Minnesota’s north shore.

Thermochrons, transectsThermochrons, transects

Thermochrons are dime sized devices that measure and store thousands of temperatures. A contact sensor is later used to download the data.

‘‘Board’ versus ‘air’Board’ versus ‘air’

Sea breeze by day …Sea breeze by day …

Land breeze at nightLand breeze at night

Normal PrecipitationNormal Precipitation

• Everywhere in Minnesota…– Summer is wettest

– Winter is driest

• North shore ‘bands’ most apparent fall, winter– Warmer lake provides energy and moisture

winter(DJF) spring(MAM) summer(JJA) fall(SON)

Snow fraction peakSnow fraction peak

Tettegouche SP transect

Let it snow!

lake superior north shore climate jim zandlo state climatology office dnr-waters 2006

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