Explaining variance in the MABL (30 m data)

In the table below are graphs showing how one C130 30 m variable varied with another. For example, to see how the neutral drag coefficient varies with distance from shore, click on the entry in the neutral drag coefficient row and the offshore distance column. Data from lowlevel legs of all flights were used, though runs whose ogives didn't converge were discarded (about 40%). BL height from vertical profiles is referenced to the lowlevel runs by averaging the heights within a 15 km radius measured during the same flight.

If the variables are correlated at the 95% significance level, the correlation coefficent is given unless none exists ("No"). A subjective description of the variables' relation is given for each combination. Correlations with BL height could not be calculated due to NaNs. Before computing the correlations, the mean of each run was removed from that run's data.

For each of the variables, click on its name (in yellow box) to see a histogram of its distribution and a map of the location of its extreme values. How some of the variables were obtained is explained below the table.

Some interesting results:

The direction of winds with respect to the local coastline seemed to define different regimes for fluxes, wind speeds, stability, and height of the BL. Slightly onshore flow was quite different than offshore flow.
As distance from shore increases, fluxes change and mean variables are less scattered. Wind speed and direction, neutral drag coefficient, and u_star are more variable close to the shore.
BL height differs most from its mean downstream from capes, where wind direction and speed are most variable.
The drag coefficient and fluxes varied with latitude. South of Point Conception, the neutral drag coefficient was quite high (at least 1.5 standard deviation away from the mean). In this region, winds change rapidly with cross coast distance (wind vector map, 30 m data adjusted to 10 m).
Aircraft heading is related to stress measurements. However offshore flights appear to have sampled lower BL heights.

Variable relation table
Listed correlation coefficients are at 95% significance level
	BL height (m)	Offshore distance (km)	Stability z/L	Aircraft heading (degrees from north)	Wind direction with respect to coastline direction	Wind speed adjusted to 10 m	Latitude
Neutral drag coefficient (Cdn)	No	Greater scatter in cdn near shore	Stable cdn decreases with u10 while unstable increases	Offshore-flying cdn lower than onshore	.2	Once questionable data is excluded, cdn increases with u10<6 m/s and u10> 6 m/s -.23	High Cdn in flights south of Pt Conception -.15
u_star	No	Greater scatter in u_star near shore .25	zeta varies most for low u_star	Offshore-flying u_star lower than onshore	.No	u_star increases with u10 .55	-.21
q_star	q_star_more negative with shallow BL	q_star becomes more negative offshore -.35	q_star tend to have same sign as zeta .7	No	No	-.13	q_star may become increasingly negative from N to S
t_star	No	t_star changes from pos to neg at about 75 km -.21	t_star has same sign as z/L .25	Offshore-flying t_star_lower than onshore -.2	t_star_ most negative for offshore flow	-.1	t_star may change from positive to negative from N to S
Stability	No	No		Offshore-flying zeta_lower than onshore	No	No	No
Wind speed adjusted to 10 m	u10 decreases with BL height	Scatter in u10 decreases offshore .15	Slowest winds in unstable conditions	No	u10 max for winds aligned with coast		No
BL height (m)		No	No	Lower BL were sampled during offshore flights	BL deepens as winds blow more onshore	Shallower BL are slower	No
Change in wind speed along the track	No	Winds are more variable close to shore -.25	Most variable winds along track when unstable (?)	No	Winds aligned with coast are most variable	Stronger winds change faster -.15	Most variable winds are downwind of capes .14
Change in wind direction wrt coast along the track	Direction may change faster for a shallow BL	Near shore, direction changes more rapidly	No	.12	Off shore winds less variable in direction than onshore	-.18	Direction varies fastest downwind of capes .18
Froude number	Deep BL is subcritical	Subcritical by 150 km from shore	No	No	Supercritical only when aligned with coast	Supercritical u10>10	No

Explanation of certain variables

BL height - the height of the MABL determined from aircraft profiles. The mean of the nearest measurements of BL height on that flight (within 15 km of the point) is used.
u_star, t_star, q_star, zeta - Calculated from high rate fluxes.
u10 - Wind speed adjusted to 10 m using the formulae in Fairall et al.
Change in wind speed along the track - To measure how the wind speed varies, du/dx where x is along track distance, was calculated.
Offshore distance - The distance between a point and the nearest point of a coastline database.
Aircraft heading - The direction the plane flew towards, measured CW from true north.
Wind direction with respect to coastline direction - The coastline direction is the alignment of the nearest 50 km of coastline to the point in question. Wind direction wrt coastline direction = wind direction - coastline direction. Offshore flow is between 0 and 180 degrees (plotted as greater than 360 degrees for clarity).