CHAPTER 10
Advanced PMVSHADE
and PMVSUN
Applications
|
T |
his chapter illustrates practical applications of PMVSHADE and PMVSUN. We proceed by looking in turn at each of our three thermal comfort conditions: MINTMP, MAXTMP and AVETMP*.
MINTMP has a dual personality because it refers to the average monthly minimum temperature and, as described in Chapter 11, sometimes provides a good guess for the dew point temperature. (As weve learned in previous chapters, dew point temperature is one of the two essential ingredients for estimating PMVSHADE as well as PMVSUN.)
Outdoors leisure thermal comfort in this
book takes into consideration light summer clothing, sedentary activity and
absence of wind and is defined as shade and sun the latter only
applying to the MAXTMP condition.
Applications discussed below draw from
tabulated data of previous chapters together with information of Chapter 11 and
Web-site-based climate data described in Appendix 4.
MINTMP Applications
MINTMP can be
described as having a dual personality as suggested below:
PMVSHADE at MINTMP, described
in Chapter 6, relates to leisure thermal comfort during the early
morning.
MINTMP sometimes provides an estimate of dew point temperature. Accuracy of
such an estimate commonly depends on high precipitation levels (as explained in
Chapter 11, pages 193-215). When historical values of dew point temperature are
unavailable, we may cautiously substitute MINTMP. (Note: historical
MINTMP data are available from more sites than are historical dew point
temperature.) Baudette, Minnesota,
page 186, exemplifies our use of MINTMP for estimating dew point temperature.
PMVSHADE at MINTMP for Any Month
Table 6-1, pages
114-123, displays MINTMP thermal comfort values by month, city and state.
The Biological Clock for Mammals
is Light Sensitive
Roosters, as well as some mammals have a
biological clock, known as circadian rhythm. This helps them anticipate
sunrise, which benefits them either in their role as prey or predator. Sunrise
is important for maintaining or resetting this biological clock.
In common with other thermal comfort tables,
out-of-range values in Table 6-1 are ignored (that is, replaced by a . Symbol).
Alaska is conspicuous in this regard because tabulated MINTMP thermal comfort
values are out-of-range for all twenty-two Alaskan cities listed and for all
months.
PMVSHADE at MINTMP in July
Table 6-2, pages
124-133, displays climate data for July and is sorted by PMVSHADE at
MINTMP (see grayscale column). From
this table, we can select a narrow range of thermal comfort values on either
side of neutrality. Upon looking at this narrow range, we see cities from such
states as Arizona, Florida, Hawaii, Louisiana and Texas.
Dew Point Temperature
May Be Estimated from MINTMP
If dew point temperature is unavailable
to us, we can sometimes estimate dew point temperature from MINTMP if MINTMP is
available. In such case, it is also desirable to have PRECIP available. See the
following discussion for details.
MINTMP as an Estimate for
Dew Point Temperature
As explained in
Chapter 11, page 193, average monthly minimum temperature is sometimes found to
closely match dew point temperature. Punta Gorda, Florida,* is one example for which dew point
temperature and MINTMP are virtually identical. Often, however, this is not
the case.
As an example of how to estimate dew point
temperature as well as PMVSHADE and PMVSUN from MINTMP,
lets now look at a city included in the NOAA database. Referring to unedited
July historical climate data for Baudette, Minnesota, (obtained from the NOAA
Web site described in Appendix 4, pages 243-244), we find July data for four
consecutive years, summarized in the table below:
|
July Climate Data for Baudette, Minnesota |
|||||
|
Year |
MAXTMP |
MINTMP |
AVETMP |
Dew Point |
PRECIP |
|
1996 |
75.4 |
53.9 |
64.7 |
57.4 |
1.56 |
|
1997 |
77.1 |
55.2 |
66.2 |
59.0 |
4.19 |
|
1998 |
77.4 |
54.4 |
65.9 |
56.8 |
|
|
1999 |
78.2 |
56.9 |
67.6 |
58.8 |
|
|
Mean |
77.0 |
55.1 |
66.1 |
58.0 |
|
Obviously, the sample size in this table is
small compared with the ISMCS fifty-year averages. Nevertheless, one must do the
best one can with what is available, and make allowances accordingly.
We may estimate PMVSHADE by two
different approaches, as described below, depending on the use of either MINTMP
or dew point temperature, respectively; next, availability of these calculated
PMVSHADE values enable a follow-on estimate for PMVSUN.
Approach 1: Only MINTMP Is Used
(and dew point temperature from NOAA Web site is ignored). Table
11-3 in Chapter 11 (pages 206-215) displays difference values of MINTMP and dew
point temperature. Positive values in the table denote that MINTMP is greater
than dew point temperature and conversely for negative values. Looking at the
table for Minnesota during July, we see that difference values range from -2
through +3, which is a narrow range compared with many regions of the United
States as shown by the table.
A Minnesota map shows that Baudette is
slightly north of International Falls and that International Falls is a little
further north of Duluth (for example, refer to the on-line map Web site listed
on page 244 of Appendix 4*).
The difference value for International Falls is -2; the difference value for Duluth is -1. Because Baudette
is so close to International Falls, we are safe in assigning a difference value
of -2 for Baudette. This suggests
that dew point temperature is +2ΊF higher than MINTMP, or, approximately:
Dew
Point Temperature = 2ΊF + 55ΊF = 57ΊF.
Taking ambient
temperature to be 77.0ΊF (that is, mean MAXTMP) and dew point temperature to be
57ΊF, then interpolation within Table 8-1, page 162, yields:
PMVSHADE
= -0.37 or, after rounding, -0.4.
Approach 2: Dew
Point Temperature Is Used Directly.
Taking
the dew point temperature value (58ΊF) directly from the Baudette July climate table,
page 186, and then interpolating within Table 8-1, page 162, and using mean
MAXTMP = 77.0ΊF as before, we get:
PMVSHADE
= -0.35, or, rounded, -0.4.
Next for the MAXTMP
condition, compute PMVSUN by first consulting Figure 9-4, page 182
(for July), and then visually estimating MRTSUN to be about 94.
Use Equation 9-1, page 173, to compute PMVSUN as below:
PMVSUN = 1.26
= -7.4022 + 0.5988 x -0.4 + 0.09475 x 94
Thus, after computing PMVSUN =
1.3 (after rounding), we see that Baudette, Minnesota, qualifies as a comfort
paradise in July, in terms of both shade and sun. Golfers and fishermen can
enjoy the superb July outdoors leisure thermal comfort conditions at Baudette*.
In summary, the above example illustrates:
(1) how to estimate PMVSHADE from Table 8-1, page 162, either by
first using MINTMP to estimate dew point temperature, or using dew point
temperature directly and (2) how to use the PMVSHADE value obtained
along with an estimated MRTSUN value from Figure 9-4, page 182, (or
companion figure as appropriate) to estimate PMVSUN.
MAXTMP Applications
Numerous examples of
outdoors leisure thermal comfort applications relate to the midday temperature
at about 3:00 PM local standard time for shade and full sun.
We illustrate below how
to determine MAXTMP leisure thermal comfort, taking into consideration PRECIP
and snow depth.
MAXTMP applications
include both shade and sun; for the latter, Figures 9-2 through 9-5, pages
180-183, show the MRTSUN isotherms for January, April, July and
October.
MAXTMP coincides with midday
when the sun is overhead
At MAXTMP conditions,
we either seek shelter from the sun (PMVSHADE) or seek full exposure
to the sun (PMVSUN). We can estimate our comfort level (PMV) in
either case.
Before moving on to specific examples,
relevant tables for PMVSHADE are summarized below:
Table 5-2, pages 68-77, sorted by state
and city, displays values for each of the twelve months.
Table 5-3, pages 78-87, and Table 5-4,
pages 88-97, refer to July only and show useful associated information, such as
PRECIP, MINTMP and AVETMP. The former table is sorted by state and city, the
latter table by PMVSHADE at MAXTMP.
Tables 5-5 and 5-6, pages 98-110, are
counterparts to Table 5-3 and Table 5-4, respectively but for January instead
of July.
Table 5-1, pages 59-67, actually displays PRECIP
for each month, but only for comfort paradise sites (that is, for which
PMVSHADE lies within the range of -1.5 through +1.5 outside
this range, table entries are omitted).
PMVSHADE at MAXTMP in July
As noted above,
multiple tables within Chapter 5 display July PMVSHADE values at
MAXTMP, namely: Table 5-1 (implicitly), and Tables 5-2, 5-3, 5-4 (explicitly).
For example, we can identify a location in
July with neutral thermal comfort and minimal precipitation. Scanning the
shaded column in Table 5-4, page 89 while referring to column 1 (PRECIP) we
identify the following comfort paradise candidates:
San Diego, California
Olympia, Washington
Portland, Oregon
For these choices, values of PMVSHADE
range from -0.5 to +0.2; PRECIP ranges from 0.0 to 0.8 inches. (Note
that a nice family vacation during July could be planned along a route
traversing through these cities.)
PMVSUN at MAXTMP in July
Let us compute leisure
thermal comfort values (in the sun) for the above three cities. Recall Equation
9-1, page 173:
PMVSUN
= -7.40222 + 0.598822 x PMVSHADE
+
0.094754 x MRTSUN
Now, refer to Figure 9-4, page 182 and
estimate corresponding black globe temperatures (MRTSUN) for these
three cities. We visually estimate MRTSUN values as 110, 91 and
92 for San Diego, Olympia and Portland, respectively.
Table 5-2, pages 68-77, and Table 5-3, pages
78-87, each display the tabulated PMVSHADE (non-rounded) values at
MAXTMP (see paragraph above) for these three cities as
-0.50, -0.44 and
0.17.
Using Equation 9-1, page 173, to calculate,
PMVSUN values are found to be 2.7, 0.96, 1.4, for San Diego,
Olympia and Portland, respectively. Rearranged in order of increasing latitude
(that is, San Diego, Portland, Olympia), July leisure thermal comfort
in-the-sun values decrease as latitude increases (with longitude
approximately constant).
Before finishing the MAXTMP discussion of
thermal comfort in July, we compare PMVSUN in July for Miami, Florida.
For Miami in July, Table 5-3, page 80, lists
a PMVSHADE value at MAXTMP of 2.27 (and also lists 6.0 inches of
precipitation for July). Referring to Figure 9-4, page 182, for July, we see
that isotherm lines for Florida are poorly defined; consequently, we can
estimate MRTSUN for Miami only within a range of
temperatures, say: 110ΊF, 115ΊF or 120ΊF.
Using Equation 9-1, page 173 as before, we
compute PMVSUN respectively as 4.4, 4.8, or 5.3. Each of these
high values exceeds the P.O. Fanger scale and they lie increasingly within the
heat stress domain; counterpart heat stress values are briefly discussed in
Appendix 2.
PMVSHADE at MAXTMP in January
To find a comfort
paradise city in January, review the gray-scale column (MAXTMP) within Table
5-6 downward; this eventually leads to a group of relatively neutral thermal
comfort cities (within Hawaii and Florida, page 110). Of candidate cities,
Miami has lowest average monthly precipitation (2.0 inches) and a PMVSHADE
value of -0.55 (nice for January at midday).
PMVSUN at MAXTMP in January
We compute PMVSUN
for January in an analogous manner as was done for July above. By referring to
Figure 9-2, page 180, we estimate MRTSUN for Miami in January to be
about 90ΊF. Using this value together with the above PMVSHADE
value of -0.55, Equation 9-1 yields: PMVSUN = 0.8.
Miami, Florida in January, is a comfort
paradise in both sun and shade.
PMVSHADE at MAXTMP for Any Month
As another example,
assume that family members are planning a northward tour of North Carolina in
April. Table
3-2, pages 31-40,
suggests only traces of snow for cities along the planned route:
Wilmington-Raleigh-Greensboro.
Table 5-2, pages 68-77, sorted by state and
city, lists the April thermal comfort values (non-rounded) for these cities as
-1.06, -1.53, and -1.94, respectively. Next, we see that the influence of
sunshine causes these thermal comfort values to improve significantly.
PMVSUN at MAXTMP for Any Month
For April MRTSUN,
we estimate a common value of about 85ΊF (by reference to Figure 9-3, page
181) for each of the three North Carolina cities discussed in the previous
paragraph. Calculated (non-rounded) values of PMVSUN by use of
Equation 9-1, page 173, are 0.02, -0.26, and
-0.51, respectively.
These sites qualify as comfort paradises in the sun during April.
In addition, Table 3-1, pages 21-30, shows
the expected average monthly precipitation for Wilmington, Raleigh and
Greensboro during April (2.9, 2.8, and 3.2, inches, respectively).
PMVSHADE at MAXTMP Paradises
for Any Month
Table 5-1, pages 59-67,
displays the average monthly precipitation (inches) for each city and month for
which the PMVSHADE index lies within the band of -1.5 through
+1.5.
For both Wilmington and Raleigh, North
Carolina, this table shows that April offers the least precipitation. (Because
the table cell is not empty, this month is also a comfort paradise month
as are May and June.)
Table 5-1, page 63, excludes
Greensboro, North Carolina, as a PMVSHADE comfort paradise during
April.
As another application example from Table
5-1, consider Tustin, California, page 60. From April through November, this
city qualifies as a PMVSHADE comfort paradise. Precipitation there
varies only from 0.0 to 1.3 inches.
In summary, by reviewing Table 5-l, we can
readily identify our outdoors comfort paradise for almost any month of the year
throughout the United States.
AVETMP Applications
In this section, we
discuss outdoors leisure thermal comfort for the early evening temperatures,
which occur around sunset. AVETMP is the arithmetic average of MINTMP and
MAXTMP. This is typically family time when family members enjoy outdoors
leisure time together after dinner and neighbors can socialize.
AVETMP often occurs slightly after sunset
To estimate PMVSHADE at AVETMP, we still must assume an overhead
barrier or tree canopy even if influence
of the sun is minimal or non-existent. Otherwise, surface heat radiation to the
clear night sky will conflict with our assumption that MRTSHADE is
equal to the air temperature.
At about this time, fans also watch their
favorite outdoors spectator sports events (like baseball or volleyball) and
campers gravitate toward their tents and stoke up their campfire.
The following tables display AVETMP leisure
thermal comfort information:
Table 7-1, pages 136-145, is sorted by
state and city and lists PMVSHADE values for each month.
Table 7-2, pages 146-155, shows associated
climate data for July and is sorted by PMVSHADE.
PMVSHADE at AVETMP for Any Month
Table 7-1 displays
monthly PMVSHADE values at AVETMP sorted by city and state. This
table is useful because it shows the month-by-month leisure thermal comfort
values in the early evening for various cities. A quick scan of this table
identifies the early evening thermal comfort value for a particular city and
month.
PMVSHADE at AVETMP in July
As an example, to see a
sampling of July 4th comfort paradise sites for viewing after-dusk fireworks,
scan downward along the last (grayscale) column of Table 7-2 to find neutral
thermal comfort values. For example, looking at a more narrow range of PMVSHADE
values, say, -0.5 to +0.5, more than sixty cities are represented among
some twenty-six states with Richmond, Virginia (see page 151) at the exact
neutral point.
For whatever application (for example, to select
a host city for a July convention, or to view a fireworks display), Table 7-2
is a convenient way to identify an ideal comfort site. Moreover, this table
also displays associated MAXTMP, MINTMP and PRECIP values. ■
